There are apparently two for the FM stereo to mono fade-both are linked somewhere here.
(There is also a TSB for the FM antenna amplifier- not sure that is posted)
I'd take the older one to the dealer- it doesn't require them to verify the failure prior to ordering the new radio- of course if yours is actually doing the fade pretty repeateably, no problems-
Hey- post the links in a reply- it might help someone in the future.