Route wires into cab?

[Bavanew]

I have a couple of questions regarding the best route to run some electrical wires.

I have a hardtop tonneau cover that is equipped with a 12v interior light and a power lock.

What wire can I tap into for a continous (ignition on) 12v supply?
I can feed the wire under the box by going behind the rear tail light assembly, but once unde the box, where do I go?

Also, I need to tap into the passenger side electric door lock.
I know that the wires are located under the platic door step cover as I've already identified them. How do I route the wires into the cab to connect to those wires? I know how to go through the firewall, but I don't want to go from the box to the front firewall and back towards the passenger door, unless I have to!!!
Do I have to drill under the door step to access those wires?

Any advice would be appreciated.....

Thanks,

Blair