A newbie seeking guidance on dulcimer finishing

Can anyone provide me with some advise on finishing. I am presently building a Folkcraft Mountain Dulcimer fram a kit. I am pleasantly pleased with the results, I choose to use Tru-Oil Gunstock Finish by Birchwood Casey. My questions are (1) do I finish the fretboard or leave it unfinished (2) on my next build (which I already have aMcSpadden Kit from the Dulcimer Shoppe) it is proper or benefical to finish the inside of the instrument? Thanks in advance for any input or recommendations.