First, congratulations on the score!

There is a difference between oxidation (patina) and filth/grime. I think that it's really gross when a cymbal has decades of Lordonlyknows, just my opinion. Anyway back to your question - I find that soaking a disgustingly dirty cymbal in a solution of hot water and dish soap works really well. Not much dish soap, and I use a plant-based one like Seventh Generation. An overnight soak followed by using a non-scratch sponge (soft side) can do the trick. Gently follow the lathing lines. However, I have let some soak much, much longer (changing out the water daily). You retain the oxidation this way, but most of the grime goes away.

I say leave it. It has good mojo and good stories to tell.

When I acquire a used cymbal, I clean it with Windex and paper towels. This gets off all the surface dirt and grime, but doesn't mess with the mojo. Sometimes you'll need to do it several times, until the paper towels are clean. Anything that doesn't come off with Windex, I just leave, because I think it's supposed to be there.