A heat pump is just a normal HVAC with a reversing valve (and maybe without the furnace part, if you're not worried about backup emergency heat). How hard could it be??
I mean, I guess I get it if you're installing it up North in a building that previously only had heat without AC, because it means you have to do all the load calculations and stuff. Plus, you may need to retrofit ductwork because your heat was hydronic with radiators. That, I admit, is a big job.
But where I am in the South, it seems like it'd be simpler, if anything, because it means you can just cap off the natural gas line and not have to deal with it. Otherwise, (unless you're doing insulation improvements at the same time or something) it's a like-for-like replacement of the AC that any building around here definitely already has, and which any normal HVAC technician ought to be able to do.