"I don't know anything about this stuff"

That is why you should have a professional install it. My husband and I can do quite a bit DIYs, but you have to know when something is beyond your skills, physical ability. and knowledge. We had a new furnace installed last year and we never could of done it ourselves. With all the computer components in the new furnaces it would of been impossible.

Someone that is intellectually gifted, and has a lot of time to learn how to do it could get the job done. The amount of time it takes to do so is prohibitive for most people. The quality of the install, how well it works, will be proportional to the time spent in learning how to do it. If you make a mistake, it could be dangerous so a novice should file a building permit and have it inspected.

Needless to say, since it is mid December, if your furnace is broken you are not going to be able to do it quickly enough.

What kind of fuel does your furnace burn? What is the input btu rating and what is the efficiency? How old is it?

Reasons why:

Building codes need to be followed.

Manufacturer's will not deal with unlicensed people for any warranty.

Parts deemed defective will be tested (most likely) especially If you are unlicensed (HVAC Contractor license in most states is required.)

If you buy furnace over the internet, read the warranty fine print of who ever you buy it from. Each manufacturer has a clause within warranty section that voids warranty if the system is purchased on line.

Without proper installation, warranties are void. If you install it yourself this falls on you or whomever you get to install it for you.

Your house is worth how much?

How much less is your house worth with a non working heating system and possibly AC system to boot.

For these reasons it's typically not worth it when you consider all the tools you will need to buy in order to do this one job correctly.

( It's illegal to do work for someone else if you are unlicensed / uninsured to do the work required. It's not illegal to do the work on a home you own, but the risks of everything that can and will go wrong is all on you.)

While the warranty isues are significant, I'd be more concerned about safety issues - fire, gas, CO. If you kill yourself (and your family) or burn your house down, not a good deal.............

I know these guys charge an arm and a leg but they've got you over a barrel.

Having a furnace installed by an unlicensed AND inexperienced person is a really, really, really bad idea. It's not like replacing a broken toaster where you unplug the old one, put the new one in it's place and plug it in again. Installing a new furnace is a custom-crafted task where the actual furnace equipment is just one part on a list of of what needs to be taken care of, often changed, and often hand-crafted (sheet metal parts) and manually assembled and then safety tested before the project is done.

If your savings won't cover the cost, the only reasonable alternative is to take out a home improvement loan so you can pay over time to hire the right licensed professional to do work that needs to be done.

Check energy efficiency programs through your local utilities and your state. They may offer rebate programs that are often tied to subsidized or paid energy evaluations. They often have loan programs that are paid at a rate of the calculated fuel savings. Contact local energy raters that should be aware of these programs, RESNET and HERS are good places to start.