Nope. I would put the new furnace on hold and go for the central air first...
I would plant a much wider variety of fruit trees...
I would grow more tomatoes...
... and maybe a small tobacco crop to horrify the neighbors--and then use it all to make bug spray the next year.
Wow! just think of the things I could grow if suddenly I lived in zone 4!
Including a formidable briar hedge to keep the migrating nits from lalaland out...
An Osage Orange hedge would work really, really well! Any migrating nits that somehow manage to git through that (which I seriously doubt), you can pitch them softball size “oranges” at ‘em. (they ain’t soft, by the way)(ouch!!!)