None of the good shops in this area are "convenient" unless you live close to them. Bruce's go to indy, Green Motorsport is a 45-50 minute drive (without traffic, but this is NoVA and that's never the case) but definitely sounds like a great shop. RRT is out Old Ox Road, 35-45 minutes away from Manassas without traffic, with traffic...double it.
http://www.yelp.com/biz/rrt-performa...tenance-dulles
http://www.greenmotorsportservice.com/
But really, for a PPI I'd search on Bimmershops for one that is convenient to where the car is and have them do it. As long as they seem reputable, a PPI is a PPI.
And big +1 to Vas' ZHP! Might have more miles, but definitely would trust purchasing a car from him rather than a used car dealer. Plus, a higher mileage ZHP with the big ticket items completed and still in great condition interior/exterior wise is a better buy.