[mreid]

If this is a high efficiency unit, it will have at least two leds that blink trouble codes. They will tell you what is wrong. You don't say if it is gas or oil, but I'm assuming gas. Since it doesn't come on at all, if you opened the unit (removed a panel) you may have tripped the interlock. Make sure they are properly reinstalled. Finally, when you figure it out all parts can be purchased online for a fraction of the retail price. I bought a new control board for one of mine several years ago for 1/2 the price the hvac guy wanted. Good luck!