I just recently tried to replace my digital thermostat for my furnace/central air. It is 5 wire system. I could not get a lit display. Does the power come from the furnace? It appears I somehow lost the
24 VAC power on the wire labeled R. Is it possible I crossed wires that could have tripped a breaker in the furnace. The furnace is a newer Coleman (2 years old) that is installed in the attic.
Unfortunately I have no A/C right now and it is quite warm where I am at.

If you did not turn off the power to the furnace, there's a good chance you've blown a fuse on the furnace control board.