ES1025,
Hmmm ... some of the response are subjective on my part so I'd cherry pick the various responses you'll get. Divot's remarks are solid concepts, which just illustrates the delicate balance of this hobby between art and science.
1. COOKING TIME: Honestly, between ambient conditions and the vagaries of each hunk of meat, I think the time would be accurate for a bone-in 8-10lb pork butt. I find a ton of 8-12 lb cryovac bone-in butts locally so I tend to stick with that; the last one I did (8.5 lbs, 225 degrees, outside temp in the mid-80's) took right at 13 hours to hit 175 for sliced ... if you're looking at pulled you'll go to 200-210 degrees. The stall point will make you doubt your sanity but ride it out.
2. INJECTION: I've experimented with injections with both pork loin and pork butt; when you've got a reduced amount of fat it does help but most butts have ample fatty goodness to work with. I do, however, like adding a bit of internal flavor as I'm partial to sliced pork rather than pulled pork. A simple pork injection could be something like apple juice, table salt, sugar, Worcestershire, and some lemon juice ... if you want, I can post the measurements under Recipes; I actually use a spicier injection on occasion with some Sriracha added for a little kick. My gut would be determine the flavor profile and the final prep (sauced, un-sauced, type of rub, etc.) and make your call based on that.
3. WRAPPING: When you wrap you can damage your bark (one of the best parts of pulled pork, IMO). The stall is actually a useful part of the rendering process so I'd simply stock up on good beer and let the meat choose it's own adventure.
4. WATER PAN: It doesn't hurt, but a spritzing with apple juice or a mop (I've actually used everything from homemade mopping sauce to soft drinks for this) are all you'll need. The water pan will primarily help create a stable and moist environment but only imparts minimal flavor to the bark ... a more direct method is better if you're looking for flavor enhancement.
5. WOOD: 6 oz of wood is fine ... this really depends on what type of wood you'll be using. I love apple, peach or cherry for this so I might actually do 4-5 ounces of fruitwood and then do a 2 ounce reload as the meat gets to 140.
If you can let us know the weight of the butt and the if you're pulling, slicing or chunking the finished product, as well as what type of wood, I can give you a bit more.