Whatever amp and sub you have - I have an old clarion 250, and a planet audio zetar 10". Both from my old vehicle, not made anymore.
pull off the AC control trim from the dash, pull strait out, top first.
remove 2 screws from bottom of silver trim/radio bezel. gently pull around the edges to get a finger in on the top side and them pull off. Key is just dont pull away to far in one spot.
Remove hazard connector and set aside
pull wire harness from back of screen.
Splice in wires on the LOC to harness. I actually installed a RAX jailbreak so I spliced into their side. I highly recommend the Rax and its good because you dont have to cut factory wires.
Wires go like this:
Red - continuous power
Black - ground
Gray /light green stripe - rear right
Gray /dark green stripe - rear right
Green /light green stripe - rear left
Green /yellow stripe- rear left
Pull power from battery to back of cab through main wiring harness, no pic. Dont actually go through the harness, just use a screwdriver or your hand if you can to go to the outside of the boot going through. If it leaves a little gap, just goob it up or tape over it. DONT GO THROUGH THE HARNESS BOOT! Route power through space behind radio, lots of room there.
Drop RCA, power and remote power wire from radio down and through the right side of the dash. Route wires to the back of cab through bottom door plate trim. You dont have to pull it all the way off, you can just pull up the inside edge and slide it in.
I just have the wires loose right now in the back. Still looking for a solid ground and trying to figure out if I am going to try to hide my amp. Right now it is tacked on the back of the amp. I may figure out a quick disconnect solution so I can pull this out if I need the room.
Build a box and install sub and amp.
Finish tucking wires, Mount gain control and put the trim back in and you are good to go!