Bob,

As matty said, you need to bring this to a shop equipped to handle refrigerants.

ALL auto A/C refrigerants are damaging to the environment, and it is illegal to vent those refrigerants while making a repair.

I am also a DIYer, and I am somewhat familiar with A/C systems, but this is one area that requires some very expensive equipment to do the job correctly, so I leave it to a shop with the appropriate equipment.

If you still want to do the hands-on stuff, bring the car in to be evacuated, then do the repairs/replacement yourself. Then, as a last step, replace the dryer, and then drive the car to the shop again to be recharged. This way, you are doing all the mechanical work, but you are leaving the handling of the refrigerant to a shop equipped to do the job.

Good luck.

Ken