Replace the evaporator unless you have reason to believe there is some
existing problem with the compressor.

The compressor should be protected against refrigerant loss.

Shop around. $1200 is way too high. Look up retail evaporator prices at
grainger.com and see how much profit they are making on a few hours work.
These guys use licensing and collusion to avoid competition and rig prices,
and then convince themselves they are worth it so they can sleep at night.