I am looking to replace the A/C compressor on my 87 vanagon.  I had the system switched to R-134A about 2 years ago, worked remarkably well and quickly cooled car.  Last fall I began to hear some noises from the compressor (it was original), so removed the belt.  I got a quote from a local shop (Eugene, OR) that does good work and understandably if they are going to fix it they want to check everything, which requires taking out rear cabinets to get access to expansion valve, etc.  This would be pricey.

My questions:

Besides installing a new compressor, what would I need to do to make sure the rest of the system is not compromised?

Where can I get a compressor? 

Any good links on DIY would be great.

Thanks!