[350HP951]

Any place that sells parts (Pep Boys included) will have compressor oil. Stick with R-12 as long as you are able to find it and the price is not so incredibly high as to make it cost prohibitive.

No one vacuums a system for 24 hours and it isnt even close to necessary. For that matter no AC machine I have ever used (and that is a bunch from RobinAir, Snap On, etc) would vacuum that long if you wanted it to. They are all auto shut off.

If converting to R-134 the correct way (and you will see me say this throughout the summer) is to remove the compressor, dump the oil, remove the condensor, have it flushed and even better have it professionally cleaned, replace the AC lines (will have to be made but any AC shop can do it for very little), etc, etc. There is no way it is worth it to do it right, you save nothing.

If you want to do it yourself just go get an IMACA test or MAC test and take it. It costs less than 20 bucks and you can buy R-12 like the rest of us. Get a vacuum pump and a compressor, set of gauges and you are good to go. If you want to do it often look for shops that are closing, most have R-12 machines they no longer use and will sell cheap (this way you can do proper recovery).