Freon leak
 

The a/c repair place think I need a need evaporator. I just refilled the freon for now. How much would a replacement cost? This is the second refill in 3 months.

They should be able to prove it with a dye leak test.
Cost of installation (involved) may very cost more than the evap core itself.

genuinevwaudiparts.com

They did the dye but couldn't find the leak in the engine. They said it was probably the evaporator.