2005 Lincoln LS AC Compressor

Hello,I have a 2005 Lincoln LS with AC problems.  Recently the AC started blowing warm air.  I had the DCC Valves replaced about 3-4 years ago.  I took the car to the dealer to have it looked at so they could tell me what is wrong with it.  They informed me that the compressor is leaking and this is the root of the problem.  I doubt this and I now feel like I wasted my money on their diagnosis.  After they informed me of this, and that it would cost $1,500 to repair, I took the car home to check it my self.  Pulled the tire off to get to the low side port.  Hooked up a gauge and the pressure was fine, which in theory, means it should be blowing cold air and it is not.  Went back to the dealer to ask them about this.  They called the tech up to come talk to me, he seemed very annoyed with this.  He told me he put his light on the compressor and saw a leak and that the system could not hold pressure, which is why it is not blowing cold air.  I told him what I found and then he said that the internals of the compressor were probably bad.  If that were the case then how could my pressure be fine when the system is running and the compressor is engaged.  If the internals were bad then the compressor would not be able to create a suction and bring the pressure down to where it is supposed to be.  They did not give me an answer after I asked them this.  I feel like they did absolutely nothing for me, except try to get a $1,500 repair.  Has anyone had this problem before.  Would it be bad DCCV's again.  Could there be valves inside the compressor that have failed.  Any insight would be helpful.