Came home to a very cold house (50 degrees!) this afternoon. Heater on, but blowing cold air. Went up to attic, took top and bottom panels off unit, and looked for pilot light to be out, or anything out of the ordinary. Can't find anything that looks wrong, or like it should be lit. I see the gas line pipe, with three "holes" that look like they should have flames going towards the middle of the heater. No flames, though. Should I turn the heater back on and put a lighter to it? I'm scared...

Should I turn the heater back on and put a lighter to it? I'm scared...

No your unit is spark or electronic glow bar or hot surface ignition and there is NO pilot for you to light. The best you can do is turn the circuit breaker for the furnace off and back on in the main electric panel and this will cycle the unit circuit board. Then set the thermostat to heat and say a prayer. If it starts working great but if not call for On Site service first thing in the AM. It might be a cold night where you live but when you said you were scared that tipped me off to the fact that you have no business servicing your unit other than what I told you to try above. Bundle up and if you have some electric space heaters now is the time to turn them on.