Originally Posted by
AlmostTrick
You could get stuck with a bike from CL that needs work ($$$) since you don't know how to properly inspect it. Beware of bikes that look beat up and well used. Having said that, the Trek 800 DVC45 linked above looks and sounds like new. You should be on your way to see how it fits.
+1 Be very picky about what you buy used on CL since you don't know anything about bikes. Look for those bikes that really look pretty much new or lightly used. There are deals out there you might have to be quick to them and have a little patience. That link looks to be very promising and it has a ridged fork which is a bonus.