Complex sentence: This period of instability ended with the arrival of David Bumbaugh, who served from 1988 to 1999, when he became professor of ministry at Meadville/Lombard Theological School.
Split into simpler sentences: This period of instability ended with the arrival of David Bumbaugh. Bumbaugh served from 1988 to 1999, after which he became professor of ministry at Meadville/Lombard Theological School.