Good luck Nik! I'm glad you are moving forward with it. The knowledge and experience you might gain from repairing/restoring this scope is worth more than any money you might get for it. I think that's what most people are missing here. It's a wonderful opportunity to learn more about how these work. And then when you are ready to upgrade, you will have a better appreciation for these pieces of equipment and how they work.
First step should be to get access to the service manual. You likely will be able to find it free online. One thing I like to do when referencing online service manuals is keep a bunch of tabs open of the manual - one for the schematic I'm looking at, one for the parts layout of the board, one for the theory of operation section I'm working on, etc. Much easier to utilize the manual this way when you are working on the scope. That way you are not constantly scrolling from sectino to section. But at the very least, a read through of the manual on where the most dangerous/high voltage sections of the scope before you start would be a good idea.
-Frank
Frank Mashockie