Gas and Oil Home Heating Furnaces - DIY Furnace Install

I looked around the forum, but, didn't see any comment regarding furnace install by homeowner. (I did see that AC install is not advised nor even possible without certification.)

How difficult should furnace replacement be if the new gas furnace - in my case a horizontal unit - fits up to the existing plenum? Can a truly handy person pull this off?

If the new unit is rated the same as the old, go for it.

Thanks for the response-
I'm considering a 90%+ unit for several reasons, including eliminating the need for possible chimney relining. Not sure of existing furnace rating, but will check. I was told that a new 80% may require the chimney to be relined. Can this be as simple as just sliding a new properly sized unit in, securing the plenum and hooking up gas and electric and venting (chimney relining if necessary for 80%) using the existing connections?

I infer from your response that if I choose a unit with a different rating the project becomes more complicated. Is this correct? Will the different rating affect existing ducting and venting? What else? I want to make a wise and cautious decision on this project. Thanks in advance...

go for it attitude.However you should check the Pennsylvania gas codes.If you plan on doing all the work on your own it could pose a problem.PDF