Here is my plan:

I want to keep running r12 but I need to fix my leaks and replace all the seals first. but before any of that I want to see if the system is functioning correctly.

I want to pull a vacuum on the system and then fill it with 152a and dye to find all my leaks AND test the rest of the system.

What do I do about oil with the 152? Should I check the level at the compressor when it is empty? Just add a little for good measure? What oil should I use?