Friends... I come humbly again to the masters for some guidance. The situation, my 1982 300D, 131K original, SUPPOSEDLY a new compressor that SUPPOSEDLY blew ice cold when I bought the car, but didn't seem to when I picked it up. I guess I assumed that it probably just needed a refrigerant charge so I never gave it much thought. Miami seems to not be cooling down any as the summer approaches so I'm really needing that AC now. (just a sidebar, I also have vacuum issues so I'm only getting air out the side vents and up by the windshield...I'm sure that'll be another posting in the near future) So, today, a buddy of mine, who's a little more savvy than I on these things (which isn't much) tried to hook me up by giving me a little R-134a charge.. unfortunately his bottle didn't have any gauge so I couldn't see what the existing pressure was before he put some in, but it was taking it VERY slowly. He disconnected the bottle, and the system didn't seem to be cooling any better (ambient air). We stopped thinking it probably needed WAY more so I went and bought a few bottles, one with a gauge. Before anything I connected the gauge, and the needle shot up into the red (Dangerously high- Have professionally serviced) zone.

My questions:
1- I thought this system could use R-12 OR R-134 without conversion... did I mess anything up? I'm not sure if anything was converted, and honestly didn't look at the sticker on the compressor.

2- What SHOULD my refrigerant pressure be between for a normally operating system?

3- Is there some sort of high pressure cut-off that disables the compressor if there's too much charge? I haven't ever actually heard the compressor come online, before or after today.

4- Do I REALLY need to take the car to some schmo to have refrigerant bled out or is there a safe way to do it myself? I understand the ramifications of letting it into the air or by flame and whatever else.

ANY help or advice would be greatly appreciated. Thank you!