Oh yes, definitely worth servicing - these movements are fairly well known, particularly as they have roots in the venus 188, so servicing should not be prohibitively expensive either. An insurance value typically carries at least a 25% premium over the sale price, so once that is factored in it definitely makes the watch worth keeping up and running.

I like the Heuers of this era on perforated leather straps personally, and I think a good quality one (Hirsch etc) in black leather would suit this 7721 well. Occasionally, we see original Heuer buckles up for sale too, so that could be a nice addition if you can source one - I've actually had strap and buckles from Australia, I think there is a fairly healthy Heuer community down under.

I remember my first watches being manual, but I soon ended up with quartz watches too, particularly as the LCD craze was in full swing at the time. Still, some of those early quartz watches are interesting too. Some made it into the Heuer range, and even my beloved Carrera had some quartz models:

We often read of people inheriting watches in sad circumstances here, it's an unfortunate fact of life with these older watches but I think wearing the watch is a great way of remembering the original owner. Enjoy this one, I think it's a great entry into Heuer ownership, just as Heuer intended.