the only unfortunate thing about buying used transmissions or anything used at that point, is you dont really know what kind of condition its in. As far as car parts from craigslist, i wouldnt buy anything on there because there is a bunch of people trying to scam people. UNLESS the transmission is still in a truck that you can drive and test it out that way, theres not really any for sure way to see what kind of condition its in without taking it apart, and im sure hes not going to let you take it apart before you buy it. My more professional answer would be try a junkyard and look for a junkyard special, because they at least will know whats wrong with it, if anything and how many miles are on it etc. Best of luck finding a new one! I had mine go out at 213,000 miles and it cost me about $1200 out the door for the rebuild.