Speaking from experience, a decent entry-level set up for servicing costs minimum $500, you'll need to do it several times to get it right, you'll probably break the first watch you try it on, and you'll forget the skills involved if you don't keep servicing watches. It's kind of fun, kind of frustrating, and only worth it as a one-off to understand how a mechanical watch works unless you plan on rehabbing watches as a hobby.
As an alternative, I recommend buying an old pocket watch and dis/reassembling that. Easier to work with, same basic principles of operation.
