#3
if the cavity for your squier isnt big enough, you'de have to make it so it could fit. then rewire everything.
just buy a better guitar. or if your really adamant about changing pickups, just drop hotrails in there. it all depends on what sound you want.
#4
It's pretty much certain that your Squier is routed HSS at least, so it should be just a question of changing your pick guard - however, Epiphone pickups aren't brilliant in my experience.
#5
I don't think it would be worth the effort just to put some random epi bucker in there. It's always possible though.
Gear
Fender Thinline Telecaster Deluxe

1983 Aria Pro II XX Deluxe Flying V

2007 S101 EGU34

1963 Kay Vanguard

1964 Kay Vanguard

AXL Badwater SRO

Hondo Strat

1974 Acoustic(brand) 134 4x10 combo

Epiphone Valve Jr.