I have smoked four turkeys so far this year, all with good results. Three were in the fourteen pound range (my preference), and the one that I smoked today was twenty-three pounds. The three fourteens all took around three hours, and the large one took about five-and-a-half. I ran my temp around 325 using lump charcoal, with apple, and cherry wood for smoke. These turkeys were all pre basted, but I also have brined them myself.

one gallon water
one half gallon veg. broth
one bag ice
one pound kosher salt
one pound sugar
whole black peppercorns (hand full)
(this is a rough approximation from Alton Brown)

dissolve salt and sugar in water and let cool
add rest of ingredients including turkey into bucket
I keep mine in the garage for at least 8 hours
before smoking, season the turkey. I go under the skin and then put veg. oil on the skin, then season that too. Also I stuff the cavity with apples and oranges. I think this keeps the breast from cooking too quickly, along with infusing just a little more flavor into the meat.
cook the turkey till the breast is in the mid 160's but make sure the thigh hits at least 170 ( in my experience, the thigh cooks faster than the breast). and let rest, tripple wrapped in foil for an hour before carving

If you have any questions, pm me, and we can talk.
I know this sounds like alot of work, but trust me, the results will not dissapoint.