need a lesson in A/C

So I have absolutely no experience with the older A/C systems and compressors, other than how to take them off of my core engines and take them to the scrap yard.

as some of you have seen, i picked up a 1978 dodge monaco with factory A/C. it appears to be in tact, but only blows hot. i haven't messed with it a ton...i really don't know what i'm looking for to see if it activates? and also if it needs recharged, if much goes into changing the freon? or converting it to the newer stuff, or if it's even worth messing with on this car. the only actuator valve i see actually looks more like a heater core blockoff?

part of me wants to yank all this garbage off of it, and the adult in me reminds myself how nice A/C would be if i can keep this a respectable driver, and have functioning A/C.

so any pointers would be appreciated. again it's a 1978. everything looks factory.