Well looking in my dell manual it states that only qualified personnel should replace a mini pci wireless network card - it mentions that this is due to FCC rules.
But then goes on to tell you how to do it
btw - the signal on my .b adaptor seems to hover around %74 - even when i'm upstairs in the room next door to the access point - or if i'm down here in the sitting room.
I have no idea about the rest of your questions - I only just got my laptop... I just thought I'd mention the thing about the FCC rules tho.