I installed both of them just above head height, and both rooms are very comfortable with good air flow. Heat pumps in general operate at a much lower temperature than gas furnace, so some people think they are not as warm, but they will get the space to the same temperature, they’ll just move a lot more air to do it, rather than rely upon the radiant heat of a mass of fairly hot air.
I honestly couldn’t say, as I was doing this with my brother. But here’s what’s involved:
The exterior unit either hangs on a wall, or sits on a pad like a regular condenser. It will require either 110 or 220 electrical service, depending on size. It will also require a smaller cable to the interior unit that powers the fan and controls the operation of the exterior unit. The main connection between the pair is the two copper lines, one larger, one smaller, known as a line set.
Most of the interior units are designed so that only one hole has to be drilled for the line set, the small electrical cable and a condensation drain to the outside. Usually you only have to drill a 2" hole (plus the holes necessary to mount the interior unit on the wall).
You’ll have to add either a single or a double breaker to your electrical panel for the unit, plus wiring between the panel and the exterior unit.
You save over a forced air furnace by not having to install any duct work, or a separate thermostat, or build a space to hold the forced air unit.
There are too many variables to give even a ballpark. But they go in a hell of a lot quicker than any other type of unit, which means that a lot of people will try to talk you out of it - less equipment + less labor = less profit.