Peter wrote:

The bottom line as someone else wrote is to find and use a well
qualified and honest HVAC contractor.

Can someone explain why you need a contractor to install a furnace?

If you're a real red-blooded, meat-eating man who knows how to swing a
hammer, turn a wrench and wire a branch circuit, then you most certainly
can connect a few wires and bend some sheet metal and get a furnace
installed, and most of the A/C as well (assuming you need a new A/C
unit).

If I could wind back the clock and play a role in installing my furnace
and AC, I'd install a bypass duct so that my furnace fan doesn't have to
blow air through the AC coils in the winter.

If I *had* to buy a new furnace - then I'd buy a new furnace, gut the
**** out of it (rip out the electronics, ECM motor and ignitor) and
install conventional AC motor and standing pilot light, then I'd install
the thing myself.