Very easy, I would recommend a couple pounds of C4 and a hammer the size of your dead cousin's uncles dog.
Remove inside door handle and window crank handle, remove inside door panel, remove vent window and channel assembly, remove window.
Take the tank down the pump is placed inside the tank on the top of the tank
Absolutely.
Pull back the clip that retains it & just pull upwards. If you pry, be careful not to scratch paint.
C20 was Chevy's designation for a 3/4 ton. 2500 was GMC's designation for a 3/4 ton. Basically they are the same.
from a library
SAE 10W30
134 freon
Yes.
Might say on title
3/4 ton.
Before 1998 - no. 1998 and after - yes.