wiring an amp to a 2001 mach 460?

I'm wanting to put an amp and some subs in my
new mustang with a mach 460.

Looking for tips and advice on where to wire
the amp in at, right now thinking the high
level speaker outs from the head unit, because
I've heard that the low levels are used for the
factory amps?

Also any tips on removing the head unit would
be nice. It looks like pry off the trim and
it screws in?

Thanks

sam