Give it 1hr/lb for a 250* cooking temp at the grate, but as long as you don't procrastinate on the foil, wrapping should make it go a little faster. I'd foil at 160-165*, and speaking of foil, I'd foil the pan as well and skip the water. Water in the pan inhibits bark formation.
Since you're planning on wrapping anyway though, cooking at a higher temp won't hurt a thing. Personally, if wrapping, cooking at 275* like Chris R. mentioned would be my plan so I wouldn't have to start as early. Have fun though, whatever you decide to do. You should enjoy the results much more than those puny "briskets" you mentioned smoking before.