after studying AC systems for years, before it became a mandatory working item for my wife and i, it finally became clear to me how it worked, and it wasn't as complicated as i thought it would be.
this was in the few years after the OEM's converted everything to R134.
so for a few bucks invested in gauges, and fixing a vacuum pump that was tossed in the scrap barrel at work, i had all the items necessary to do repairs.
first order of business was an auction minivan with a cycling clutch, but warm air.
going through that, it was discovered a line had a slight groove wore in it, so new line[s] o-rings and a drier later, it blew 40 degree air !
nothing like success to urge a guy on !

since then, i have graduated to detecting leaks with the ultra-violet light and system dye stuff to removing and replacing complete dash assemblies for evaporator replacements. [not fun, and ALWAYS replace the heater core while you are in there with a QUALITY replacement.]
as i found out [or learned], it's not as hard as it appears if you research what it takes to do the job first, then take your time doing the actual repair with copious notes, diagrams [if necessary], and pictures if you need them. a FSM is helpful as well.
if i can do this successfully, you can too !