I'm sure there are some simple HVAC (heating, ventilation, air conditioning) books in the local library. Or buy online. Or something like About.com might have material.

Furnaces are pretty simple though the recent push for efficiency has brought computers into the mix (ominous music goes here) and spark-initiated fireup rather than pilot lights.

We changed out our furnace last Spring and the new one is much less fixable than the old.

Something to consider is if you do fail to get the furnace to go and the house will go to ambient you'd best find a way to drain the plumbing (potable water - your hot water heating system should be filled with anti-corrosion/anti-freeze??? treated water) to minimize pipe damage and water damage upon thawing.