LTBMW is always crazy busy. The guys there are always running around and answering calls (emails too, I'm sure). If it takes a long time to get back to you, don't take it personally. Calling is the easiest way to get ahold of somebody, but since it's not the best option for you, send Long another PM. I PM'd him a week or two ago and I noticed that he has not logged into his moderator account for a while. Send a PM to his vendor account and he should be able to get back to you faster (again, give him a few days).
They don't discriminate. They are happy to work on any car, whether it be a 328i, M5, or anything in between.