Hello,
My ac clutch doesn't engage at all. I have a leak in my compressor, I know this because my dealer but dye in it and it leaked out around the rim of the compressor.

I know my compressor needs to be replaced (and the system vacuumed and refilled), but should anything else be done? Is it possible for me to do the compressor myself and take it to an ac shop to flush and fill it?

You should be able to do it yourself.

The compressor will not turn on if the pressure is low.

I've seen new compressors on ebay for like 2-300 dollars. Should I go this route or the junk yard ($40) route?

Tough call if you want to take a gamble on a used and possibly seized one from the JY.

See if you can get a guarantee from the JY for it so you can get your money back if it is shot.

Haynes says I should replace all the fittings and orings and even the accumulator when the compressor is replaced. Is all this true?

More than likely.

have you done this?

have you done this?

No, but logic will state you are better off doing the job properly rather than cutting corners.

If something happened to your old compressor to make it leak out or fail, it is possible due to refrigerant contamination from bad seals or the compressor turned itself into a whole mess of metal powder. Or rather, because the seal is gone and you lost refrigerant charge, it makes it easy for moisture, fine dust and other contaminants to get back into the system.

It makes sense to replace your accumulator because it may be full of crap you do not want to circulate and cause pre-mature failure of the compressor again. O-rings and lines are a cheap insurance policy against leaks and cracks that later could fail and put you back in the same place again. However, this is just informed opinion. I never had a system completely fail on me, in my experience. Had them leak plenty of times, but O-rings and seals along with new banjo bolts, etc. always seemed to bring them back to life. Good luck!