Bought a mountain dulcimer at an estate sale

It was 75% off the original sale price and I figure I would clean up/refurbish/repair (not sure what to call what I am doing and I hope this is the right place to post).  The main damage are cracks on the top board of the sound box.  Any advice on how I should do this?  I'm thinking that I have to remove the top and fix it from the inside.  Here are some pictures. (see pix in followup post)