Get 2,3+ Estimates from the dealers. No one can tell what the cost of You replacement will be. Some areas are super expensive, some are cheap; sometimes replacing your line-set is a pita; equipment... Every job is different.

What is your location? Location would indicate whether the area is consider high cost installation. If you have very cold winters, or very hot summers it would suggest buying a 95% efficiency furnace, or a SEER 16 AC.

For your size house, I would think the cost would fall into the $5000 - $10,000 range. The low end would be single stage lower efficiency (80% AFUE and SEER 13 or 14), and the high end would be 2-stage higher efficiency (95% AFUE and SEER 16 or 17). HVAC contractors are extremely busy in some areas, and material costs have increased due to COVID-19. I suggest you get quotes ASAP before the winter begins when HVAC contractors are answering no heat calls.

You can estimate the wholesale price of the equipment on the internet HVAC sites. That's roughly what the contractors pay. Anything above that is their loaded labor cost.