I'd appreciate some help on my Seamaster De Ville

I inherited this watch from my late father-in-law, and took possession of it when my mother-in-law passed away in 2014. I'm finally able to turn my attention to it and could use some help in determining: 1) it's caliber and year; 2) best place to have it serviced; and 3) advice on getting the bracelet lengthened. It needs about 1/4 inch more length. I was able to get it on and it did wind itself enough to run for a while, and it kept very good time. I did gently attempt to wind it but the crown was pretty stiff so I didn't proceed. I did not attempt to pull out the crown to set it. It appears to have a screw-in case back and I've made no attempt to open it up.

I'm the furthest thing from an Omega expert, but from what I've been able to find it looks to me like a caliber 711. Omega's vintage watch section gives a date of 1962, which would match the period my f-i-l was likely to have purchased it. Unfortunately I don't have any family info on the exact year. It is possible that he purchased it in Switzerland.

Thanks in advance for any help!

Sorry for the small photo size. This is my first forum post and I resized them too small. Here's one larger, I'm happy to redo the others if anyone needs me to.

Hi @Jeff S,
Nice watch.
I am no expert but I hope this helps and I am sure the more knowledgeable members will chime in.
The only way to confirm the calibre is to remove the case back, it will be on the movement. You should also find that the case back will be 18k (0.750) like the band.
As for the date of the watch it can be roughly correlated to the movement number, the other way to confirm is to get an extract from Omega.
I don't know how you would lengthen the band sorry.
Wear it well and with good memories.
Cheers