[Restoration Q] Longines Automatic Ultra Chron watch that belonged to my Grandfather.

That's a very nice watch. Personally, I wouldn't touch the outside, just get it cleaned up a bit and maybe a new crystal. That will keep it in the same condition as last worn by your grandfather.

These were made from the late sixties into the mid seventies. There should be a serial number on the movement that can help date it, once you get it opened. The movement should be serviced (it's a Longines caliber 431 I believe), high-beat. I don't know anyone there, but I'm sure you have a competent watchmaker in a city that size. The movement service shouldn't cost more than a couple of hundred, barring the need for any hard-to-find replacement parts. The watch will be worth more than that, but this isn't a high-value vintage piece, and the real value is as a family heirloom.

I don't believe that the watchband is original, but you can easily find a very nice leather strap to complement the watch. Kelaran on ebay makes some good ones.

Good luck with it & post some pics when you're done!

Welcome to the OF!
Fully agree with Darlinboy...a "clean and service" with a new strap will make this piece stand out. I am not sure what the availability of original crowns is like for this model...the experts will chime in soon!