Definitely join the PMA forum on here. That is where I got tons of great info for our first PMA trip. Here is a link to my trip report about the Hairy Lake PMA
As the PMA Turns... The information about obtaining a PMA permit is quite variable and seems to depend on which ranger you get. I had no trouble calling up the ranger station that oversees the Hairy Lake PMA and reserving the permit ahead of time. However, other people have been told you can't reserve a permit and that you have to request it when you pick up your regular BWCA permit at the ranger station. This has left some eager campers permit less, so I recommend trying to get someone on the phone who will write you into the reservation book.
Note that you MUST pick up your regular permit and the PMA permit at a ranger station. An outfitter cannot issue a PMA permit. Also expect to get questioned more about Leave No Trace as well as your general wilderness experience level.