2003 Cadillac CTS Bose AM/FM 6cd changer

Interior problem
2003 Cadillac CTS 6 cyl Two Wheel Drive Automatic 75000K miles

I am having a problem with the FM stereo fading in and out and the cd changer does not work. I am prepared to repair or replace the unit (it is one unit). The dealer says they can get a replacement if they have the PART number or they send it out for repairs to a GM authorized shop. The repair shop says that unit is not available anymore (even if the parts dept. At the dealer says it is), so they would have to repair it, but need to do an estimate first and if it is unrepairable would replace it with a "reconditioned unit" that they can't (or won't tell at what cost). As you can see I am getting the run around here, so I went to several car audio places and got the same response. Frist we have to take it out etc. Etc. So I go on e-bay and find one there that has a U2R interchange. My car has a U2S interchange (build code). Will it work? I don't want to have the unit taken out and get a bunch of suprises no matter which way I go-replace, repair or e-bay. Thanks for any guidance. I know the easiest thing to do is take it out, but that's why I'm on this site. I could probably get it out, break something in the process and then things go downhill from there.