A couple of issues you can run into replacing a hood with an over the
range micowave unit.

A dedicated power circuit.

If ducting outside will the exsisting range ductwork match the needs of
the microwave ?

Clearance between the range and the bottom of the microwave.

Stud location in the wall behind the range impacts ductwork installation
and microwave mounting points.

The cabinet above the range, is it secure / strong enough / at the right
height / wide enough / too wide to use as a mounting point for the
microwave.

I've done two over the range installs. Both were not easy but worth the
end result.

Also my current unit goes brain dead after a power glitch requiring me
to unplug it , wait awhile, and then replug it into the socket in the
cabinet above the unit. You want to have easy access to that plug.