Gas and Oil Home Heating Furnaces - Need furnace advice

We just purchased a 2500 sq ft home that was built in the 1860's. Currently there is a "low efficiency" furnace in the home and no AC. The current owner explained that before they moved in a few years ago the previous owner disconnected the ductwork to the 2nd story and added the current wood burning stove they use to suplement the upstairs heat. The 2nd story dustwork is still in place but does not run to the furnace located in the basement.

I do not know where to start. According to the homeowner the furnace does work but not enough to heat the entire home.

Can AC be added to the current furnace? Can another unit be place to the die of the other to heat the 2nd story? Should the heating/AC unit be placed in the attice to run the 2nd story?

What are the entire costs? I need to make this as inexpensive as possible but want it done right the first time? If we were to do the duct work and get the units at costs what are the costs?

Any help or info on types of units and intallation would be appreciated.

Idealy a unit in the attic with new ducts for the 2nd floor would be best. It sounds like the existing furnace is pretty old and the only way to truly know what will work properly is to get a few estimates from proffesionals. I always reccomend local contractors since the box stores are just going to sub it out to lowest price guys in town.Use the companies that have been around for a while. Be sure they do a load calculation on your home.

Do get 3 bids for the same job. like Matt said Id go for 2 units one up and one down. As far as cost its so different all over cant say.

ED ;)