No power. power up to cicuit board with on off switch. no lights on panel.

disconnect the switch you put in and try it, sounds like there could be a short, did you work near anything that might have got bumped? turn on the vehicle and see which cicuit the problem is in by using your test light or multimeter on each cicuit untill you can find the one giving you the trouble, sometimes wiring harnesses wear and you get an open short, start at your battery and check every connection all the way to the back noting condition of the wires, no easy fix on this sorry, check the second fuse box under the hood along the firewall as well if yours has this

since how long are you facing the problem

check fuse on cicuit board.

Possible that the power supply has failed which is a switch mode power supply. So switch off, remove power cord and open the panel and look at the SMPS cicuit.
Use a multimeter to probe, start checking from the fuse.
Click on:

http://www.fixya.com/support/r5826301-working_switch_mode_power_supplies

It may be in safety shutdown due to short cicuits in the power supply or in the backlight inverter board, those are the two areas you need to check first.
If you are going to DIY and have proper tools, electronics knowledge, and know safety precaution then please read on:

Please see my basic troubleshooting guide here:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide

http://s807.photobucket.com/home/budm/allalbums

http://en.wikipedia.org/wiki/Capacitor_plague

Parts: www.shopjimmy.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx

Please post back what you find.

your cicuit is overloaded. hook the DW up to its own cicuit, or at least one that will not overload it. Circuits should not be loaded to more than 80% of their capacity. 15 Amp load no more than 12 amp.
when motors/pumps start they use the most load or power, or when your DW turns on the heat.

Sounds like you have an open cicuit in the oven power. The control for the gas uses the impedance of the hot surface igniter. Check for a circuit breaker. The wiring diagram should be inside the control panel cover.

Just to be sure you checked fuses underhood? There is a junction block at rear of truck on frame it can cause lights to not work check it to make sure all conections are tight.also check the trailer hook up for brake light power as this is on a seperate cicuit but is supplied by brake switch.If you have power there it will eliminate switch.your fuse box has a brake fuse and trailer brake fuse

You most likely have a power supply problem. but the problem may not be the actual power supply. The drive cicuits for the plasma panel can load down the power supply and give you the symptoms that you are having. Without being able to be there and take voltage measurements, I'm afraid I can't narrow it down more than that. My first suspect is that one or more of the sustain boards (the boards that drive the plasma panel) have failed. That would explain the lack of display. It is likely one of 3 boards that has failed, PSU (power supply) logic (the main control board for the set) or DE2 (panel drive board). There is a chance that the panel itself is bad, but that is not the most likely cause of your problem

We regularly repair these control board assemblies for only $32.50 nationwide, and that's much cheaper than replacing the board. For safety, disassembly and other info see http://tinyurl.com/yzjozk