<PAGE>

                                                                 Exhibit 10.14.2


                      AGREEMENT AND PLAN OF REORGANIZATION
                                AMENDMENT NO. 1
                          DATED AS OF:  JULY 15, 1999


          This Amendment No. 1 to that certain Agreement and Plan of
Reorganization by and among PaeTec Corp., a Delaware corporation ("PaeTec"),
PaeTec Merger Corp., a Delaware corporation ("Merger Sub"), and Campuslink
Communications Systems, Inc., a Delaware corporation ("CCS"), dated June 4,
1999, is agreed to by the parties as of July 15, 1999.  All capitalized terms
used but not defined herein shall have the meanings given to them in the
Agreement (as defined below).

                                    RECITALS

          A.  PaeTec, Merger Sub and CCS which are the sole parties to that
certain Agreement and Plan of Reorganization dated June 4, 1999 (the
"Agreement"), wish to amend the Agreement as set forth in this Amendment No. 1.

                                     TERMS

          NOW, THEREFORE the parties agree as follows:

          1.  Section 2.2(c) of the Agreement is hereby amended in its entirety
to read as follows:

               "(c)  the Certificate of Incorporation of CCS immediately prior
               to the Effective Time will be the Certificate of Incorporation of
               the Surviving Corporation, provided that Article Fourth thereof
                                          --------
               shall be amended to provide that the total number of shares of
               all classes of capital stock which the Surviving Corporation
               shall have the authority to issue is one hundred (100) shares of
               Common Stock, par value .001 per share."

          2.  Section 5.10 of the Agreement is hereby amended in its entirety to
read as follows:

               "5.10  CCS Stockholders Meeting.  CCS shall call a special
                      ------------------------
               meeting of its stockholders for the purposes of voting upon the
               approval of this Agreement and the transactions contemplated
               hereby as soon as practicable, but in no event later than
<PAGE>

               September 15, 1999, provided, that CCS may, in lieu of holding
               such a meeting, obtain such approval by written consent of
               stockholders in accordance with the requirements of the DGCL.
               CCS shall take all reasonable actions necessary or advisable to
               secure the vote in favor of such approval."

          3.  Section 8.11 of the Agreement is hereby amended in its entirety to
read as follows:

               "8.11  CCS Stockholder Debt.  Concurrently with the Closing,
                      --------------------
               PaeTec shall have (a) paid in cash (by wire transfer of
               immediately available funds to accounts designated by the
               applicable payees) $5,250,000 of the indebtedness owing to
               certain stockholders of CCS (as designated by CCS prior to the
               Closing) and (b) executed and delivered promissory notes ("PaeTec
               Notes") in favor of (i) those Persons designated by CCS to
               evidence the assumption by PaeTec of indebtedness of CCS owed to
               such Persons, and (ii) other applicable stockholders of CCS for
               the amounts specified in clause (iii) of the definition of the
               term "Net Working Capital" less amounts paid by PaeTec pursuant
               to the preceding clause (a).  The PaeTec Notes shall (A) be
               subordinate (on terms reasonably satisfactory to the parties) to
               an expected $70 million senior credit facility of PaeTec and be
               in the principal face amount of the outstanding balance of the
               applicable assumed indebtedness on the Closing Date, which amount
               shall in no event exceed in the aggregate $7,500,000 less the
               amount paid pursuant to clause (a) of this Section 8.11, (B) bear
               interest at 8% per annum (subject to adjustment from time to time
               to reflect changes in the prime rate of interest charged by City
               National Bank), and such interest shall be paid quarterly (unless
               PaeTec shall be in default with respect to any senior
               indebtedness, in which case interest shall be accrued but unpaid
               for the duration of the default or until maturity), (C) provide
               that they may be repaid in full or in part from time to time, at
               the option of PaeTec, without premium or penalty, and (D) be
               payable, together with all accrued but unpaid interest to date of
               repayment, upon the earlier of (1) the consummation by PaeTec of
               one or more financing transactions with aggregate gross proceed
               of $5,000,000 or greater (whether debt or equity transactions),
               or (2) June 30, 2002."

          4.  Section 9.16 shall be amended by adding the words "PaeTec made a
cash payment pursuant to clause (a) of Section 8.11 plus the amounts for

                                       2
<PAGE>

which" in the third line of such Section 9.16 after the word "which" and before
the word "a".

          5.  Section 11.8(c) shall be amended by adding "(a)" before "$13.8
million," at the end of the fourth line of such Section and adding the following
language after "$13.8 million," in the fourth line of such Section:  "plus (b)
the outstanding principal balance (and any accrued but unpaid interest thereon)
of the borrowings, if any, approved by PaeTec, plus (c) the outstanding
principal balance (any accrued but unpaid interest thereon), if any, under the
CCS Note."

          6.  All references in the Agreement to a Voting Agreement, when used
with respect to or in connection with any Stockholder other than Alliance, Kline
Hawkes or ULLICO, shall mean a Representation Letter, in the form attached
hereto as Exhibit A, to be executed and delivered by such Stockholder.

          7.  Except as hereby amended, the Agreement shall remain in full force
and effect.

          IN WITNESS WHEREOF, the parties hereto have executed this Agreement
and Plan of Reorganization as of the date first above written.

                                                PAETEC CORP.


                                                By:  /s/ Timothy Bancroft
                                                   -------------------------
                                                Name:  Timothy Bancroft
                                                Title: Vice President - Finance


                                                PAETEC MERGER CORP.


                                                By:  /s/ Timothy Bancroft
                                                   -------------------------
                                                Name:  Timothy Bancroft
                                                Title: Vice President


                                                CAMPUSLINK COMMUNICATIONS
                                                  SYSTEMS, INC.


                                                By:  /s/ Joseph J. Golden
                                                   -------------------------
                                                Name:  Joseph J. Golden
                                                Title: Chief Executive Officer

                                       3