Dave...no one can really give you a price without a lot more information. I would have to see your house. Need to know what kind and size of furnace, your insulation, would need to see your ducts, in order to know if they are adequate. Also would have to check out your electrical service to see if it is adequate. Need a lot of information.
But....in a perfect world with a 2800 SQFT house installing a 3.5 or 4 ton ac unit..12 seer into a perfect furnace set up perfectly I would expect the cost to be around $1800-$2100. If anything is not perfect expect the cost to climb.