First off, get a digital proble thermometer. You'll never know if a butt is done without it, and you don't want to keep opening the ECB and stabbing it with a instant read.
Dont listen to Bill here... A but is about the only thing I can tell is done without a probe. Check it every hour or so checking sometime just before you think it should be done (you gotta open up the cooker once in awhile to mop it anyway). When it's good and done, it will have pulled back from the bone quite a bit, plus it should just about fall apart when you try to pick it up with tongs.
That said, a probe makes it easier. I like to pull my butt at 205, but usually only wait until 195 (who can wait, it smells good, and we're all hungry). The difference is that at 205 the thing just falls apart when you go to pull it. Unlike some of the guys here, I also pull the butt within about 5 minutes of taking it out of the cooker.
I dump ashes in my compost heap, but you could dig a small hole in the back corner of the lot, or just spread them around the shrubs and rake it in good. Just be carefull because the PH of fresh ash is bad for some plants plants that like acid soil (is that right?). If you compost it you don't have to worry about PH.
Or like Bill says, build a catapult and send the ash to the jerk neighbor (if you have one) by airmail.