My radio went into the dash (without modification to the dash metal)
and looks oem. My graphic equalizer went in the glove box. The amp and
CD changer both went into the trunk.

For the radio and graphic equalizer, I used a tap at the fuse box for
pwr source. It's a brass fitting (think upside down question mark
without the dot) which fits between the end of a fuse and the fuse
contacts in the fuse block. The straight end sticks out and a female
blade type connector slides onto it. Available ad a lot of auto parts
stores.

The amp gets it's power from a dedicated line which runs from the
battery + terminal, through the firewall, inside the frame rail,
through the right rear fender to the amp. This was using an amp
connector kit, available at Radio Shack.

When the radio is turned on it turnes on the graphic equalizer, which
sends a signal via the blue wire to turn on the amp.

As for which wire is positive or negative, that depends. Different
manufacturers use different means. If the wire came with the speakers,
it "may" have two different size blades; the wire may be marked with
plus or negative signs along it's length; one wire may be copper and
the other silver; etc. while it is important to have the correct
positive lead, it's even more important that both leads be the same;
both leads to positive having the line or not, and both leads to
negative having the opposite.