If you are not in Bossman's area, this helped me out
http://www.sheldonbrown.com/straighten-chw.html

+1 on the thrift store bike. As long as the bars and stem are aluminum, your only difficulty would be guessing if the seatpost is the same size. If you had a post that fit, you could run a strip of paper around it and mark it. That would give you a closer guess. Some of our LBS have bins of cheap take off parts, $5 stems and such. Worth checking your area, but the thrift store is still probably cheaper.

Paul Bosman
(one S)
Minneapolis