Auto Air Conditioning & Heater Repair: A/C in 1999 Tahoe not blowing much cool air, evaporator, cool air

Question
I have a 1999 Tahoe LT that has dual A/C. I've never had any problems with it so far (knock on wood I don't start now) but several months ago the front vents stopped blowing as much air as the rear vents and now the air coming out of the front vents is not a cold as the rear. I took the vehicle to a shop and was told the evaporator needed to be taken out and washed due to hair and dust etc costing almost 500.00. Is there any way that I can clean this myself and if not does this sound like what the problem is and if the cost is about accurate for Florida fees? Why would the rear be blowing colder and harder than the front if it's all on one evaporator?  Please help, I'm burning up!

Answer
I doubt seriously that it is an evaporator problem as I have NEVER seen one plugged up YET.

I believe your problem is more related to the air door controllers under the dash of which will require a vacuum schematic and a vacuum gage in order to track down the problem.