Before you take your barrel in to be threaded, find another barrel that already has choke tube threads. Measure the outside diameter of the barrel muzzle of both guns with a caliper. If yours is the same or larger, there should no problem. Many shotgun barrels that were not made for choke tubes are too thin.
The next issue is what type of metal was used in your barrel. Some are a chrome / steel alloy that is really tough to thread. Don't be surprised if your gunsmith wants to charge you as much as a new barrel to thread it. After market barrels are very available for common shotguns such as Remington, Mossberg, Winchester, and Browning. A new one will run about $150 but used ones can be found for $50-$100.