I had a trusted general contractor go through my home to check out stuff I didn't know about. Charged me ~$400 and was worth the dough, for sure. Home inspectors in Alberta have no licensing requirements, so pretty much anyone can do it. That's a big problem here.
I was one of the first people around to invest in an ultra high efficiency furnace, and did so when natural gas was ~$2/gJ, so people thought I was nuts. I did it to reduce my consumption of fossil fuels, but when gas rocketed to $10/gJ or more for several winters no long after, I paid for the furnace quickly.
I have a Lennox, and despite their reputation for being so-so, it's been excellent, requiring little maintenance and no repairs. I bought it because we had a program at work with Lennox and it cost me very little to upgrade from mid to ultra high efficiency.