I could never get the engine A/C in my 1987 El Capitan to work right. It would cycle too much despite being charged, and didn't put out cold enough air. My solution? Take everything out except for the...
It's just nuts and bolts, with only a few special tools required- vacuum pump and gauges. All of the information is online if you want to learn. Attitude and patience are key, without BOTH a project like this should not be attempted. I just don't like handing my hard-earned money to someone who has no vested interest in the outcome.