Since it is a ranch + partial finished basement, the duct installation cost will not be too high. But still basically you have to install the whole heating/cooling, 20k?
2. replacing panel may mean to comform with new electric code, installing arc safe breakers--that most likely mean you have to replace most of the electric wirings, 6k?
3.Duct first.
Be careful the old heating ducts may have a*****esto.