The only thing I would add to Greg's post is that a course in Quantum Physics will help greatly once you get the manual and have to deciphrr the steps in some jobs there.
Also a huge dose in patience as sometimes just finding the job on the CD can be a lot of work just in it's self.

I actually took the time to go through mine and log the pdf numbers for the jobs I knew I was looking at performing and then I copied them to a hard drive and renamed the things so that Icould actually figure out what they were about...
Took me several days of browsing but it has paid off in the long run.

BTW - Larry's advice is excellent as I just did this with my 1980 and as it turned out I was just low on R-12. it cost me 180.00 with R-12 and labor but the AC is cold and works with the orginal parts...

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique