We are planning on getting a new furnace and central air for our home. Our current heat system is 25+ yrs old and not functioning well.
The ducts are in the slab and currently only a few rooms have heat blowing through the vents. It's a cinderblock with brick veneer ranch type home that used to have an attached garage, which was converted into a 20 x20 bedroom with a full bath. This room has it's own separate wall heater and it does have
a very small crawl space, but I don't think it's accessible. We want the new heat/ac for the whole house.

I know we will most likely have to seal up the old vents. Will we have to have the new vents in the ceiling? and if so, I'm worried that the
heat won't reach the floor, which will be cold because of the cement slab. Can new ducts be put in the walls and if so, how will that affect
the cost? Can the new system be put in the attic? The current furnace is in a closet in my kitchen.

I would be so grateful if someone could suggest some options for me so I have some knowledge before I call out a company. My husband saw
a heat/ac unit that was one unit and we wondered how something like that would work?

Thanks so much for any input.