Jet my .02 cents...
Don't fret over the rub. A simple application of Kosher salt and black pepper will provide plenty of flavor. This also provides a "base line" for future brisket cooks.
Temp: 250 is what I use. You'll find some folks who cook "hot & fast" (300+) and others who go low & slow (225) Given the untrimmed weight of 15# I'd keep it in the middle.
Internal temp: that should ALWAYS be secondary to tenderness/doneness. A piercing probe should in & out like butter. You'll find that mark to be 200 MOST of the time...could be a bit less or more depending on the meat.
Foiling: always a hot topic of discussion. Take a peek at the recent brisket thread in the FEC Competition forum. Note Coach's comments on foiling. He's on a winning streak on the Texas comp circuit with brisket and he's now a firm advocate of NOT foiling until the meat's done.
Starting temp: FEC cooks will start brisket as cold as possible, and run the FEC at low (180) temps for several (6-8) hrs to boost smoke flavor. It's not an issue with an Amerique. I've cooked brisket with both of 'em.
Smoking woods: totally subjective. If smoking a large packer in the Amerique, I'll go with 4-6 oz of Hickory. Mesquite...I'd cut that back by half.
Best advice I can provide is to keep it all simple as you learn the ropes. Keep notes and keep your tweaks minimal as you go.
Injections: Butchers BBQ makes several products made specifically for brisket, injection powder and Prime Dust. The former is mixed with water and injected. It contains phosphates which aid the meat retain moisture. Prime Dust adds flavor to the water, used to mix the injection powder. Think of an "au jus" concentrate. I always use the brisket injection; haven't made up my mind on the Prime Dust
/brisket rant