What prep is recommended to add a new finish to my older dulcimer?

I made a dulcimer in a class with Keith Young, luthier, 5 years ago or more, but never really did the finish like I wanted. Since then, I've used a cleaner now and then to polish it a bit. I learned that may not have been smart. In any event, I want a nicer finish than the one I gave it. Are there any recommendations for prepping the wood before I put on the finish? And any preference on finish? Any thoughts on Minwax?Thanks for your advice,