ligrill, if you're wondering why more folks aren't chiming in about your question, it's because buckie has spoken. He's the Yoda of low-and-slow kettle cooking, and no one wants to say anything once he's spoken. Do what he says, and you too can become a master.
Good luck with your shoulder! My only advice is to be VERY patient. As in, think in terms of whole hours... it will take about one hour for your grill to respond to your adding coals, or adjusting vents, or dealing with a change in the wind. It's pretty common for first-time cooks to do way too much fretting and fussing and (worst of all) lifting the lid to 'check on things'. Remember that "if you're looking, you're not cooking", and keep that lid down. Your grill already knows more than you do about cooking pork shoulder, so watch it and listen to it.
Also know that shoulder is pretty forgiving. If your fire is a bit hotter than your desired range, don't worry about that too much. If it dips down a bit cooler, add a few lit coals to bring it up. Just don't be in any hurry.