air conditioner conversion

I just bought a 1991 Cherokee 4x4, a follow up to my wonderful '95 Cherokee. The problem-- the air conditioner still has the old system in it that was rendered obsolete with the new refrigerant standards a few years ago.

I've read all of the hype on the 'net about what you need to change, what the factory recommends changing, etc. What I really want to know is-- who's correct? I hate the prospect of spending summer in the heat, but don't want to sink a ton of money into something that I bought primarily to go hunting in. Also, if anyone can recommend a good place to buy the parts from I'd appreciate it. Thanks.

The 1st question is why the system is discharged .Ignoring all the hype,most A/C systems will work well with a 8oz Ester oil charge and 85% R134A charge. Vacuum the system for at least 1 hour before charging. Your local parts store has conversion kits.However,if your system has leaks or component failure,compressor,evaporator,etc.,your looking at major $.