The legal issues of sending a firearm to someone else to work on aren't all that simple, that's why gunsmiths have FFLs and must log a firearm they work on into their records. Best to have it done locally or ship it to a licensed gunsmith like Wayne York. But the FAQs are chock full of DIY tips that anyone can do. Everyone's first option if the barrel is loose on the frame with the action closed and the forend removed, is to send it to H&R for repair if it's a factory fitted barrel, they can also do a trigger job on it, lots of info on that in the FAQs too.
Tim