06IS250FL

The AC on my 06 IS250 was working fine until about a week ago...then it started to blow "warmish" air. The outside temp is mid-90's but the AC definitely wasn't working ok. Throughout last week the air would work intermittently...it would always "blow" but it wasn't always real cold the way it's supposed to be. This morning when I took it to my local Lexus dealer it felt like it was working fine. The dealer says that there's a leak in the evaporator and that the cost will be $1900 to replace it (from what I've read here, it's a very labor-intensive job). Dealer says I had a 1/2 pound of freon in there when they took it out . My question is, if it's the evaporator, would it work sometimes and then not work other times or might there be another problem? Obviously don't want to pay for an evaporator if that's not truly the problem. Car has 135K miles on it if it makes a difference. Waiting to see what I hear from some of the experts here before making a decision on this. Thanks in advance.

06IS250FL

Maybe a mod can move this question for me. I did not realize that I was posting in the "Performance" Forum. I guess it should be in the general IS 250 Forum. Thanks.