You can access lots of paintball related files by ftp'ing to caticsuf.cati.csufresno.edu . Login is anonymous. Password is your email address. You can also use email to access the FTP archives via ftpmail servers set up around the Internet. Check any of the paintball magazines for mail-order companies.
Local stores are difficult to find.
Sometimes sporting goods stores will have them. Places to play and some stores may be listed in the back of the magazines. First of all, don't buy a gun until you've played with rental equipment several times. No single gun is going to please everybody, and you need to become aware of features that you like or dislike about the marker you've been renting. When you do go to buy a gun, that experience will help you be better informed about the different options available to you.