If your cycling inseam is 29.5 then you definitely need the 17.5" frame for standover clearance. I agree with Emily, the cockpit may be too short, but that will depend on the lengths of your femurs and arms, and how aggresive a position you want to assume on the bike, none of which we know. BUT, putting a longer stem on is easy and relatively inexpensive (~$29, nitto technomic comes in a lot of sizes to dial in fit http://www.lickbike.com/productpage.asp?PART_NUM_SUB='1173-10'), and will only improve handling as I think the stems on those bikes as supplied are too short (I always put longer ones on) so again given the apparent good condition and good price, I think its a good bet. Again, what about my suggestion of driving out to test ride prior to bidding?