The 480's an awful lot of motor in the MiniMag, I've the E-Flight 450 in a Blast which I think is called a Flash over there and that's a full on 3D machine and yet bigger and heavier than the MiniMag. If you're trying to take future into account the I think for the extra $20/30's you can get a reasonable motor for I'd get something a bit less powerfull but maybe as you say the speed controller that can be used in soomething else but as ozrcboy says it's hard to rip bits out of a working model, my son now flies my MiniMag. Alternatively you could sell it as a complete working ship withh the "right" bits in.
Servo's, I used out of planes I'd destroyed like the aerobord swift and Ultrafly Phantom, in essence any reasonable 9gram ish should do the job for a plane like this.
In terms of building it personally I terrible at it and as a result don't enjoy and this was my 1st attempt which scared me BUT the instructions made it so easy, the only bit I slightly struggled with a bit was the mods to the motor mount but if you get a motor that fits you shouldn't have to do that.
Batteries, I used 2100's to start with a it was what gave me loads of stick time as I was getting over 23 mins and had 3 batteries.
About 3/4 months later I thought I was "bored" with the plane and rang a hobby shop, described my ability and asked what I should get next. He gave me some of the best advice ever, increase the throws slowly, one hole at a time and slowly move the CoG back, it totally changed the plane, made it more responsive and tiedied up rolls etc but more to the point started getting me ready for the next one !!!!!!
See you've got a sim as well, I managed having flown extra's etc on that and having had my MiniMag for about 5 months and could literally throw it around in the sky to jump to an Acromaster but it was stlll a big jump !!
Good luck and let us know how you get on but again any other queries just let me know !!!!!!