Well, the heat exchanger would be the bedeviling part that could fail.
Your blower motor isn’t part of the fired unit since it’s also run when cooling is on, so replacing that wouldn’t likely trigger the rules governing your heating unit.
Maybe, instead of planning wholesale replacement, since LowNOx regs are ALREADY in place that might reduce the desireability of a new furnace model, make a phone call to a few repair companies, and build a roster of Lennox parts that “typically” fail.
Keeping spares for your existing unit could extend its life a couple or three decades, until they make repairing these units illegal, which would be the next tyrannical move.
Still, you could DIY and get away with it.
Thanks. Those are good ideas.
Yes, a cracked heat exchanger is the end of the road for furnaces. I wonder if that is a replaceable part, too?
Of all things today, the exhaust inducer fan would not shut off after the burner cycle ended!