I am a DIY'er and I did it whit the help of the manuals and some imagination. It took me about a while but, I just took my time and everything when just fine. If you do not have the time or the patience, PAY somebody to do it. Trust me!
After replacing the evaporator, receiver drier, the expansion valve and a few things under the dash that were old (i.e. vent vacuum controllers?). I just took the car in for an evac and freon charge. You may want to change to r-134 while you are at it!
BTW buy the cooper evaporator!
Do a search, you will see my name in a few those postings.
Good luck either way.