Welcome to the 645 world. I am on my second round of ETRS's.the first being in '82. Currently i own three ETRS/ETRSi bodies... price was too good to pass up.
I currently use the 40-90 and 100-220 zooms for my main shooters, though the 95mm size makes filters expensive. In back up are my 75mm and 150mm, with plans of a 40mm, and 200mm.I also just started with a 2x teleconverter,to give me what I can not get with my larger zoom. Prime lenses are coming down to the point where getting a kit together will not kill the bank, as long as you don't do it at once. As for speed grips, I would not know how to shoot without one. Even when I use the large zoom, on a monopod,the speed grip is to me, a continuation of the camera body. I do use the winding crank when on a tripod, as I am using a cable release.
For film development, I was turned onto Sharp Photo (Sharpphoto.net) by the gang at Film Photography Project Podcast. For C-41. They machine process, at about $1.50 per roll, scanning for $6.50, and shipping for $3.00 for first roll, and rest ship for free. B&W is about $7 a roll for development This is one of the best prices I have seen. This way I figure until I start scanning and developing my B&W at home,it cost about $1.25 per shot (film, developing and scanning)
As for getting film, I live in Salt Lake so when I am home film is not that hard to get, though the selection is limited. If you check out the web, you can find just about what you want for film stock.