The Ruger .22lr pistol is an easy one to thread. A gunsmith might have threaded 1000guns in his lifetime for muzzle brakes and flash hiders that are 2" long, but a silencer needs to be aligned enough for the bullet to make it 6" or more. Can not help you about this shop, I have seen them listed in phone book, but never have found their shop when I looked for them. The alignment is easy to check, once the silencer is threaded on, peek through the bore center the bore exit visually concentric to the chamber of the pistol, with it aligned like this if you can see any aspect of the silencer while peeking straight through the bore then it is crooked.
Gemtech is based in Idaho, I could be wrong but never heard of them doing threading work in Oregon.