I had a similar problem, but the old garage was already gone, I just called a bunch of contractors to have the old pad removed and a new garage built, I went with Federal Garage (885-5400), they will tear down the old one, and build a new one. Their ad says $9449 for a large 2 car (mine is 24x20) But since I’m in the city it was slightly more due to stricter codes, Kenmore is probably similar. We paid $10,500 and it was built in 3 days (1 day for demo and concrete, a month later 2 days for the build).
Don’t have to worry about any codes or crap like that.