Gas and Oil Home Heating Furnaces - Replacing old furnace

I would like to replace my existing furnace (20+ yrs old) with a new high efficiency furnace (~95% AFUE). There is no requirement where I live to have a licensed contractor to do this, so I am considering doing it myself. A permit and inspection is all that is required. Does anyone have advice on how to install one, where to buy, what brands, cautions, etc?

I replaced a gas furnace in our first house with a forced draft unit from Sears. The biggest problem I had was doing the sheet metal work to match up the ducts. Since I also moved an A/C unit to get ready to build an addition and had to have an HVAC guy in anyway I had them fix what I and a buddy had done. We made the duct too small and it wasn't flowing enough air. The electrical and gas was straightforward, I had the hardware store (an old time real hardware store) cut and thread the black pipe that I needed, which wasn't much. Gas is nothing to mess with so if you aren't sure of your ability get a pro. Mine was inspected by the gas company because one of the reasons I had to replace it (other than needing a bigger one to handle the addition) was it was leaking gas into the combustion chamber and the gas co. made me turn it off.

Good luck.

last week i had a furnace put in and the 90% + units required different than the standard units. the venting pulled in outside air to be combusted (instead of internal air) so the venting was to be on the side of the house and not up the chiminey. i decided against the 95% model so i can't help much more.