#1
ok so i recently got the seymour duncan dave mustaine pickups, and i went to my local shop to get an estimate on how much it would cost to get installed. they were charging me 95 bucks for it (including a new switch)

is this how much its supposed to cost or are they trying to rip me off?
#2
Do it yourself. Thats about right for what they charge, or you could buy a switch and do it yourself for under $1 (Not including switch)
#4
That's...odd. Usually pickups go everywhere (except if they are SC or p90s going into humbucker). I'd give it a try at first, looking well into the diagrams, and if you can't, then definitely send it to a pro. $95 sounds like a lot for me, the guy who did it for me charged $20 for 3 pups and even installed a switch for turning on the neck pup.