91 s13 complete a/c swap

[240Strong]

K so i searched it up and found different answers in each post. SO here it goes. I have the usual no cold air a/c so i go down to auto zone and pick up the retrofit a/c kit for 36 bucks not bad at all!! I complete the whole "swap" in likle 10 minutes in the parking lot and its blowing out some decent cold air. The next day however blazing hott day and no cold air... again. I got a major leak. Tried a whole can of the leak stop. To no resolution. SO enough of my story. lol I called up he cheapest place in town to geta/c work done and they want 500 bucks + to do a complete r12-r134 swap... An i cant afford half a stack just for my a/c so i wanna do it myself. So my question is... What all needs to be replaced? i heard the o rings need to be replaced the system needs vac'd out. a new compressor? and what else? Thanks guys until then.. il enjoy the 93degrees plus