Randy,
I don't know about Ford trucks but my Chevy has two auxillary power connections on a fuse block under the hood. Each has a 30A fuse. The wiring harness the factory routed along the chasis to the rear contained two extra 10awg wires. I put connectors on the ends under the hood and bolted them to the fuse terminals. One of the wires goes to the lights in my cap/shell and the other goes straight to the 12V power supply in the bed. Both are constant-meaning they are independant of the ignition harness.
If your truck has the setup mine does it would be easy enough to get a five pole connector for both the truck and trailer. Just put the constant power on one of the poles. That way you could have a dedicated circuit for charging the 12V battery in the trailer.

For 120V just take one of your extension cords and cut it about one foot from the male end. Get the appropriate size male and female cord ends and replace the one you just cut off. Drill a hole in a convienient place on your trailer and insert the cut end of the piece from the extension cord. Inside the trailer put the female cord end on the cut wire. Silicone around the cord as it enters the trailer and let it sit overnight. (It would be better to have the factory molded end outside.)(A power strip might be nice too.)

For 120V on the fly: Since you may have the battery inside the trailer a simple 12V DC to 120V AC power inverter will convert the already avialable DC to AC. A 150Watt power inverter can be had for around $35 and will last for days with a fully charged battery. I've done it in the back of my truck with the wall warts.

I have to admit it sounds pretty involved. It really isn't though. Just three things to do and you'll have constant 12V and 120V whether you're traveling or sitting under the tree in your backyard.
Remember, the simpler you make things now the easier it will be to deal with away from home. Less time monkeying around means more time flying!