A heat pump is a question about the house before it is a question about the equipment. The questions below are the ones to settle while you still have room to change course. Ask them in writing and keep the answers with the file.
Is there room outside?
The outdoor unit needs a level pad, clear space on its sides, and a spot away from where snow or runoff collects. Ask the installer where the unit will sit, how the refrigerant line will reach the indoor section, and how the pad will be set. Walk the spot yourself and check for overhead wires, a wall that blocks airflow, and any dryer vent or exhaust that blows toward the unit's intake.
Can the electrical supply carry it?
Ask whether the existing service and the panel have room for the new load, and who will confirm that. A quote that does not name the electrical work has left a question open. The electrical panel page on this site covers how to judge the panel itself.
What do the ducts look like?
Ask who will inspect the existing ductwork and what they will look at. Leaks in the supply and return runs cost comfort and efficiency whatever the equipment. Ask whether the indoor coil or air handler will be replaced along with the outdoor unit, and whether the pairing is one the manufacturer lists. A mismatch can keep the system from reaching its rated output.
How does it handle a cold day?
A heat pump gives up output as the outside air gets colder, so many homes in cold areas keep a backup heat source. Ask how the backup comes on, what controls it, and what the installer used to size the system for your area. Ask to see the load calculation. A straight answer with the calculation on paper is worth more than a verbal assurance about comfort.
What does the warranty cover?
Treat the warranty as a separate document from the installation. Ask which parts are covered, for how long, and what the paperwork asks you to do to keep coverage in force. Service contracts and warranties each have their own rules for waiting periods, transfer, and cancellation, so read those clauses in writing before you sign anything. The heat pump page on this site gives the typical service life and when to plan for a replacement.