This is best left to the professionals. You first need to recover the R-12 for recycling. That requires special equipment that a lot of shops got rid of years ago. Some shops won't work on R-12 systems for fear of contaminating their equipment.
Once the new fittings have been installed and the compressor oil has been changed, the system has to be pumped into a vacuum for at least half an hour to boil out any moisture or humidity. Next, a measured amount of the new R-134 is injected under pressure. This also requires the proper equipment.
If you do all the work, then ask a mechanic do inject the refrigerant, most shops won't allow that because they're taking on the liability for work you did. Even if nothing goes wrong right away, they know too many customers get angry when the refrigerant leaks out through no fault of the mechanic's. They did what was asked for, then, when the car owner's work caused a problem, it's the shop that gets blamed and the bad reputation.
Be aware too that refrigerant is very dangerous to work with. It can cause blindness and frost bite. Professionals wear safety glasses, gloves, and a face shield.
Saturday, August 1st, 2015 AT 9:58 PM