A/C has not worked in years. Where do I start

I have a 72 buick Skylark that has not had a working A/C in a long time. I'm ready to start working on getting it running again but before I start spending money I'd like to know what steps I should follow and what has to be changed. I'm assuming that certain parts will need to be changed or updated to be compliant with current standards regardless of what else is wrong with it. Is this true? As far as I can tell the system is intact and has not been molested--Yet.

 

Pressuer test it to see if it leaks and go from there.

 

find any leaks,must flush system,must change drier if sat or opened,check switches and condition and connection of vent tubes, clean vents, anybody else chime in,marty