Well, the first thing is that I wouldn't light it the night before. I assume you're going to cook it all day tomorrow and you want to cook it for about 11 hours and eat about 6. So, I'd get up about 6 tomorrow morning, take the butt out of the fridge and go light the fire. I'd leave the bottom vent and top open until the fire is going good. Throw on some apple wood chunks. Then I'd put on the plate setter, legs up, a pan filled with some sort of liquid (bad wine, beer, water, apple juice, etc), the grate on top and then the butt. Close the bottom vent to about 1/2 inch. Close the top and leave the daisy wheel with the hole open until the temp comes to where you want it - about 250 - and then shut down the daisy wheel holes to a sliver and the bottom vent a little more and play with it until the temp stabilizes. Let her rip! The good thing is that a pork butt is about the most forgiving cut you can do a low and slow with. About the only thing you can do is overcook it turning it into a piece of burned crap. It's done when you can pull the bone out which will probably be at 200 degrees internal - IMO it will be done before 11 hours. If so, wrap it in a towel and put in a cooler until you're ready to eat. Have fun!
What you've got is a beef tenderloin - roast it as you would a pork tenderloin to about 125 - 130 (rare - medium/rare) and rest - I'd do it direct and flip it once after about 10 minutes at about 400 so that you get a good seared crust - if it's like most tenderloins there is a thick end and a small end - the temp should be taken in the thick end - you'll get fairly well done on the small end with graduated degrees of doneness as you move toward the thick part - I'd also put a steak rub and let it sit refrigerated with the rub on it for awhile