1998 Mercury Tracer. For awhile, the heat/A/C defrost wasn't switching properly.For examle, if you had it on vent and switched to defrost, it would take awhile--more than a minute or 2--for it to switch over and start blowing from the defrost area. Then the A/C started to stop blowing cool air after it was operating mid-trip, occasionally switching the temperature dial back and forth from hot to cold or switching from A/C to vent back and forth would cause it to kick back on with cool air. Then it stopped blowing cool air all together. Finally it has stopped blowing air all together. I am thinking it is not compressor or freon, it is probably the heat/A/C radio assembly and I just need to pull it out and replace that. Yes or no?

Another fact to consider: this vehicle was in a minor accident going up over a curb and deployed airbags. Airbags have not been replaced (worth more than the vehicle). Does that affect a 'diagnosis'?

Part 2: If I do need that assembly, the part # I have is F8CF 18C858 DC and the junkyard has a part # F7CF 18C858 DK Are these 2 different part #'s interchangeable? Junkyard is over 100 miles away and is the closest one, I'd hate to go there and compare parts only to see it doesn't work, would rather order by phone and have it shipped can anyone tell for sure if these 2 are a match? Or give me resource with Mercury to call and find out? Has stereo/cassette (no CD) heated back window and A/C.

Thanks!