hey bud u are talkin to the king of this right now...i have a 94 also and just got done replacing the expansion on mine...ive pulled the evap. out about 4 timesin the last month...the first time getting that white plastic ousing out is definitely the hardest...but when u put it back (or when i did) i'd leave the crazy hard screws out cause the housing stays put with like 2 screws holding it...
there are a few copper phillips screws all around the bottom half and yes like 2 or 3 in the back up behind it...dont be afraid to yank the stupid thing...personally yelling at it and callin it names b4 pullin on it seemed to work well ;-) the bottom is easier than the top because of one bolt...its up way up in front of the housing but near the black tubing that the air runs out thru to the vents...its black and I took the vent tubing out to ratchet it out. Don't get discouraged the it does come out and the second time you do it you'll be able to get it out in 10 minutes tops...if ya have any questions lemme know...BTW if someone told you the evaporator was bad...it's probably just the 30$ expansion valve attached to it, and your evap is fine...if yours was like mine it slowly started blowing warm and then finally gave up, BUT was fully charged with freon still. (also i'm sure u know but empty the freon b4 u disconnect the evap haha, or else it'll scare the *BLEEP* out of ya!)