Do not close the door!
Yes, you can figure out the combination. A Locksmith would also service the safe and make sure everything works fine. You can just find the combination by carefully studying the dial, with the door open. You have only one chance. If you fail, be ready to disassemble the inside of the door and the lock cover.
Is not an easy task but can be done. Look for similar safes restorations in "this old safe" area of the forum and see for yourself how these safes work and are made.
Whatever you do, test the combination at least three times with the door open before closing the safe. And then let the owner try it another three time before closing the door.
Good luck
