1994 silverado ac condenser replacement

[1986c10]

HI, a buddy of mine is paying me to repair the front end on his 1994 chevy silverado that was in a front end crash. It turns out the ac condenser was damaged so i ordered a new one. I have never messed with ac systems, barely any of my vehicles have even had ac. I first noticed that new condenser had caps over the lines, i unscrewed them and they started hissing so im wondering if i can just unscrew them and let the pressurized air out of the condenser and install them to the compressor lines? Also, im hearing i have to add r134 oil to the system, about an ounce or so. Is this sucked in with vacuum through the lines or do i simply funnel it into the condenser fitting? Also, can i just recharge the system with a bottle or refrigerant from auto zone or is this whole process better left for a shop to do? Thanks in advance!