HI folks,
I'm new here.
Have a 91 Silveraado extended Cab 350 loaded. 240,000 km. I love this truck and am doing some A/C repairs. Replacing the compressor, accumulator, and orifice tube and converting to R134a refrigerant.
I have a couple of questions as follows:

1) Where is the orifice tube located?

2) How do I purge the system, before getting it charged? Or do I drive it to a shop after installing the new components and have them do the purging and recharging?

3) How much oil goes into the new accumulator, and how much into the new compressor?

I understand that I need to put the new oil in the new compressor and in the new accumulator, I'm ok with that, but I read somewhere that after doing so, I should have the system "purged" I think was the word. Then get it refilled. I do most of my own repairs, but until now have had nothing to do with A/C.

Any help would be appreciated.

Many thanks,