To clean it up buy some bore foam and let it sit in the bore for several hours, and then check the cleanliness of the bore, if its still dirty, repeat the process, next, you will need some kind of gun oil to remove all of the rust, now, I'm not going to recommend one brand over the other, so just look for a strong oil that will remove rust, also, you may want tolook into getting some gun bluing, so after you remove the pitting, you can refinish the gun. And about looking up the value, you should be able to find a website that specializes in gun identification.