Yea the worst part of taking apart the interior is the screws most times won't hold when you go to put everything back together. But the rear A/C & Heat is very easy to repair for me because it's a relatively small unit, it's when you have to replace those custom windows then you have to take everything apart.

I too am in the same boat with the A/C, I have to replace the expansion valve and so much more... But hey hope it goes well for you, I'm just fixing all the mechanical issues before I go to the A/C.