Sending to a gunsmith is a good start. You are starting with a clean slate. He may be able to bore sight it for you. If it is way off, he will find out.

Do not start a sight in from 100 yards. If your sight are way off, it will just drive you crazy. Start at 50 yards. Try 1 or 2 shots. If nothing is on paper move in to 25 yards and try again. Once you are on paper you have a starting point. If you can really stabilize the rifle and have a friend with you, fire one round; keep your eye in the scope and have your friend adjust the scope until the crosshairs are on the hole the first shot made. Shoot again. The shot should be very close.

This method saves ammo and time (not to mention your shoulder). Once you fine tune a little at short range, extend the distance in increments and continue to fine tune if necessary.

Best of luck!