First thing would be to install a new ac o-ring kit and orifice tube (since it sounds like your ac compressor clutch is working and kicks on). Very easy and straight forward job, just disconnect the refrigerant lines and put new o-rings in wherever they come out. Orifice tube will be after the condenser (the 2nd radiator thats usually mounted in front of the radiator) and before the evaporator (tube leads from the condenser to an air plenum (black box on passenger side firewall) and the evaporator is in this box). After that is just vacuuming the system with a vacuum pump and seeing that it holds vacuum for ≈ 24h, then introducing the proper amount of refrigerant. The job is extremely cheap at less than $30 in parts and very few tools needed, which is wrenches only usually (buy fluid wrenches if youre the tool collector type, also napa sells 2 sets of crows feet that are like fluid wrenches but i think i remember having issues with them not fitting on flexible rubber ac lines on my 1983 gmc). Otherwise youll need to rent the vacuum pump and ac manifold gauge tools, at autozone it will be ≈ $400 for pump and gauge rental, but all that money is returned upon return of the rental tools. Then introduce the refrigerant into the low pressure side (see pic related) until youve got the right amount of it (buy a chilton or haynes by asking for one for your car at the autoparts store).