I have a small apartment that is heated with a boiler and cast iron baseboard right now. The boiler needs to be replaced and I'm considering switching to forced hot air and adding central A/C. The boiler is 60,000 btu and more then enough for the area (about 22 x 20). The furnace would have to be horizontally installed in the attic and vented through the roof, most furnaces I see and for a vertical install. It might be possible to install it vertically in the basement but I'd rather keep it in the attic. All the rooms (kitchen, bath, bedroom and living area) can be accessed through the attic and it would be very short runs.
About what would it cost in parts for the furnace, A/C unit and whatever other major parts I'd need? It's going to cost me about $1800 to replace the boiler anyway so, I figure if I can get A/C and clear out the boiler area for the water heater which is currently in the attic and it's not going to cost a fortune it's a much better setup.
How much exactly would be involved in getting ducts down. Can pretty much everything be run through a 2x4 wall in a space that size? One room does have cathedral ceilings so I could easily get one large duct up high if necessary.