With a standard heat pump that uses strip heat in the indoor unit,
replace both the outside and indoor units. If you have an "add on"
heat pump that uses a gas or oil furnace for auxiliary heat, replace
the outdoor init and indoor coil. The furnace may or may not need
Prices vary, depends on local labor rate, taxes, cost of rent, etc. No
way anyone can give you a ball park for your area over the internet.
Get a Manual J load calculation done. Also they should measure the
existing air flow or do a Manual D duct design. Size varys with
climate, number and size of windows and direction they face. Also
insulation values in walls, ceiling and floor.
My 2000 sq. ft. ranch in Myrtle Beach, SC hasa single 2-ton system, but
I have only a little glass, (average amount for 20 year old house).
Don't let them size it by the square feet of floor area.