I have already reputtied and reglazed a bunch of our house windows, but only on the windows that were painted inside and out. I am now about to work on the wood stained windows which are in bad condition (I think someone decided in the 1950's or 60's to cover them with aluminum storms rather than repaint and putty).

I have no problem reglazing and repainting the exteriors, but dealing with the interior side of the window has me a bit stymied. The first floor woodwork looks like this:

The wood on the windows has dried out and the finish has dulled from UV exposure sort of like this:

And where it isn't dried out terribly, it is very rough and unattractive:

The questions I have are these:

If I need to fill in the wood, what filler should I use?
How do I match the filler to the wood and then stain to match, not only the filler but also any sanded areas?
I am currently thinking shellac for finish, but was the original finish varnish?

Any hints or ideas greatly appreciated.