I have a stack of similar windows that I am in the process of restoring. The process that I use is to remove all paint with a heat gun, and sanding to prepare for finishing. I then replace the glazing points and glazing compound for a tight seal around the glass, then prime and paint the frames. This general process will work well for any old wooden window refurbishing.
In your case I would also redo the sash as well, because removing the old paint will insure proper operation of the window, if it is designed to open.

Use a heat gun and scraper to get all the paint off, you can buy a heat gun at Home depot.After that use paint stripper/thinner to remove all the resedue from the paint, do not use the heat gun with the stripper!!!!!!!! Sand it in stages, start with a 100 grit and work up to 220. After that the wood should be ready for stain or paint. Believe me its not complicated but it is a lot of work. Just be careful not to gouge the wood while your scraping it.

Sounds like a sand and stain project. I personally wouldn’t even paint an antique window if I were you, but if you choose to do so, yeah, a primer will keep the paint nice-looking, as well as the wood, by creating a water-proof seal between the two.