This is by far the best site for all fountain pen enthusiasts, inexperienced or expert:
http://www.richardspens.com/ -> Reference Info
Click on "Fountain Pen Filling Systems" for info on all the common ways to refill different types of fountain pens.
B, F, M do indded mean bold, fine and medium respectively. Probably an insult to your intellect, but it refers to the thickness of the line which indirectly affects the size of your writing.
For $85, you could get just about get a nice Parker "51" Aerometric with a Lustraloy cap. eBay is your best bet. Also have a look at the Marketplace on FountainPenNetwork.com