So my A/C has been blowing semi-cool air for the past few months. I thought it was low on freon so I had a family friend help me add some without using a gauge kit. That seemed to help temporarily, but it's back to being semi-cool. In Louisiana at about 100 degrees in a black car, that's not too fun.

Anyway, we got a gauge kit and tried to add freon. The gauge showed that the low pressure was 55 and the high was 200. The manual for the gauge kit showed that the high pressure should have been around 400. This led us to believe that the compressor was just not getting the job done...

Is this a correct diagnosis? If so, how much time and money should I expect to put into this if we did it ourselves? The compressor looks like it is shadowed by the alternator, but I don't know how easy it would be to get to. My friend told me that the last compressor he did work on, he had to drain the radiator and move it out of the way and took him several evenings to get it working again (Jeep Grand Cherokee). I would expect a jeep to be harder than an Accord but I'm no mechanic so I'm not sure.

Thoughts? Alternative diagnoses?