The good news is that even if your new one fails you can still send it off for the rebuild. The last time I checked Jerry is out of spares, so you'll still have A/C during the rehab process. At $11 I wouldn't send your eBay unit back even if it's bad. I have been down this road and for the most part there are two types of units. Ones that are dead or will die soon, and ones that have been rebuilt. The only exception is the one that was in my "Q1" that lasted over 200K without ever being replaced or rebuilt. Finding one of those isn't worth the trouble... you could try 10 junk yard take-outs before you get a good one.
Nothing particularly difficult about the process. Check out
http://www.carstereohelp.com/s...o.htm
Good luck!
Heath