I suppose it would be a bit like f4rting in church for me to point out that you can buy a complete 95% afue variable speed G**dman furnace for less than your original repair quote.
So, What the original OP is going to buy one and have it delivered to his home and what, sit it in the garage until he finds someone to install it? and if they don't install it for free, well then you really are farting in the wind so to say, no one get to enjoy the smell.
"The critic is a prisoner to his own experiences and perspectives, erroneously believing his limited experiences are the sum of all truth". T.D. Jakes