Our gas furnace/central air unit is 20 years old. We had someone come out and do a safety check and tune-up and about 35 minutes in, the technician showed me some things that showed major wear and tear and quite likely safety issues. He didn't want to go any further with a tune-up since in his opinion, it really just needs to be replaced.

We have an almost 1700 sq. ft. two-story house (with an additional 750 sq. ft. of unfinished basement). Any ballpark ideas on how much a new heating/air unit normally runs?

This really wasn't a fun day.