why did my truck just stop running the switch turns but nothing?

Ignition module(TFI), ignition coil, timing chain/belt(rare), fuel pump, fuel pump relay, or EEC(computer) to fuel pump relay are all likely suspects. You need to find out if it has no spark or no fuel. You have to make sure when you turn the key to ignition that the fuel pump primes. You'll hear it run for a few seconds. If you don't hear that you have a fuel pressure issue. Either the inertia switch, one of the relays, or the fuel pump is no good. The fuel filter can cause a pressure issue too but if it just up and died on you then that's not the cause.

Seeing if you have spark is easy. Just have someone crank the motor over while you have an ignition wire off of one of the plugs and hold the plug wire to a piece of metal to see if it arcs. You have to have the wire contact close enough to the valve cover or whatever your trying to arc it out against. If there's no spark follow the path back until you find the culprit. It'll probably either be the coil or the ignition module.

The exterior lights didn't work before but they do now? Elaborate...

No one can help you if you don't give better details and timelines. My suggestion is take it to a mechanic. You sound like you're in over your head.

Dead gas pump ? *******

Clogged fuel filter ? **********

Dead coil ?

Have these digmosed