I'm not sure I qualify as the old, grizzled turkey hunter you guys are looking for, but I've been hunting them for about 15 years. This will be my first WA season, so I'm not a local expert. At some point I will head to the Colville area, if it works out and we can meet up, I'd be happy to help you all out share knowledge.
I've killed them with bow and shotgun, so I don't have a problem with either, but from experience, do your homework and practice, a lot! If you are body shooting, the vitals are about the size of a baseball and if you are a deer hunter, you will feel like you are shooting too high. The rule of thumb is "shoot them high and watch them die, shoot low, watch them go".
I prefer using a Magnus bullhead and shooting for the head. Similar size target, but you can see the head!
All that said, I would suggest taking one with the 12 gauge first. Nerves can get the best of you when one marches in strutting and gobbling!