Looks good WTN! It has a nice rustic appeal with the Tru Oil over plain timber.

re: string trees - One or two, depends on whether or not you're getting any pre-nut resonance, and an extra string tree is not the only only way to fix it if you do.
I would say most people just throw on the second tree and be done with it (I used to be one of them) but a properly cut nut can eliminate the need for a tree on the D/G strings most of the time (but not always and typically it's just the G that is the problem).

I'm not saying there's anything wrong with having two trees, it's just not necessary all the time.
See how you go with just the one, and if there's string weirdness happening, make sure the the string nut slot is angled properly or chuck on the 2nd tree if you're not confident about filing the nut.