Freon fill kits are cheap enough at a NY auto parts store. I would only add freon if there is some still in the system. Even a few ounces of pressure. My experience is usually;
Rarely is it;
a compressor shaft seal, but they do wear out after thousands of miles.
very rarely a condenser coil (in front of radiator)
even rarer an evaporator (inside car air flow).
You can rent a vac pump I am told and usually borrow tools from auto zone for a depostit.
It's not rocket science but is engineering.
Google it and soon you will have it fixed at a fraction of the cost. Never add liquid freon as it will shatter valves in compressor.
Warm can slightly NO FLAME.... And add liquid with system off. Then add gaseous only while running.
You may have to bypass the low pressure cutout to get it to come on. Return gas to compressor cools the compressor. Rule of thumb is when suction line to compressor sweats, your gauge has enough gas. Monitor air out of duct windows open on high so cooling inside car doesn't give false cooling temp. Air should cool down as suction line getss cooler. If temp starts to inch up, you are adding too much gas.
Some newer cars are tricky as they have low speed economize features that reduce pressure on compressor near idle. This Largely stemmed from gm 1976 on up cars blowing pressure lines at idle for too long. If the suction line frost up or freezes on a warm day you h as ve air or moisture in system and need to change receiver drier and vac system before filling. All cars have a lable on how much freon a specific system holds and an empty system can be filled by that amount.
My truck takes 2 pounds 4 ounces. So that's 20 ounces or almost two 12 ounce cans. See suction line or temp output. Do not overfill.