cockpit switches, leds and I/O help needed

Hi all
I would really appreciate some helpful advice on how to power my generic instrument panel and throttle pedestal, I have searched the forums but soon was lost and confused when the topic moved off from my narrow band of understanding.

Details freqently asked for by the guys offering help.

Flight Sims used.
FSX-SE, P3D and X-Plane 10 (my original remit was to have a modular system that was compatible with all 3 BUT the further I research the more difficult the project becomes and more watered down the systems have to be..so comaptible with all would be nice but not a project killer if its not possible.

Expectations for the system
It has to be portable and as modular as possible, it has to fit on a regular desk and be easily put together for use then broken down for storage. I want it to be functional for GA to Turbo Props upto Commercial jets (Airbus 3** series are my current favoured atm) with a reasonable functionality for each airframe type (at least for the main switches and levers) Modular so it can be expanded as I go along. I have a mockup of a MIP and Throttle pedestal and have the carcass diemensions to allow saitek pro flight panels to fit into the slots ( I used saitek as a bench mark rather than a plane to use these products. I would like the MIP switches to illuminate when on and create an annunciator panel. for the Throttle pedestal I would like to incorporate at least some of the switches required for A320 start up from C&D (although not realistic in real life operations it is still fun) in addition TOGA control and reverse lever on the throttle levers (already fabricated but not wired).

Hardware currently purchased (I have a small budget avail for the project if more I/O are required)
I have purchased 1x arduino uno, 1x BU0836X, 1 x un-used ATX power unit, 25x 12v illum when ON toggle, 12x latched 12v illuminated push button, 4x 3 pole 4 position rotary.

I have already made and tested a landing gear lever with working LED lights for locked and transition using JimNZ's software Link2FS-multi and the arduino uno, 2 micro switches, 3 green and 3 red 5v LEDs with the recommended resistors.

What I need is to design and built a wiring Loom/Harness to power the illuminated switches and the LED's, I do not know where to begin so I need lots of help if at all possible.

apologies for double post I did not see the Mod notice regarding the post being approved prior to it being placed on the forum I thought I had lost it and made a second post here http://www.mycockpit.org/forums/showthread.php?t=30838

I need some help with the correct wiring of 3 pin led toggle switches to a BU0836x
the pins are pwr acc gnd
I I can have the led operating on/off with I/O board B1 to pwr and I/O board gnd to gnd but there is no output from the board to the output monitor DIView
however if I connect I/O board B1 to pwr and I/O gnd to light I get no led activation but the correct ouput sent to DIView monitor. what do I need to do to get both the ouput and the led to operate when the switch is in on position.

I would like to utilise a separate power supply in addition I would like to power several switches of this type with power supplied from my ATX power unit.
any help would be appreciated