If you were installing straight A/C I would say go ahead and try it DIY with caution. A heat pump is a more technical piece of equipment that needs many more wires and controls and procedures during installation.
I know, I know people you talk to will say it's just a glorified A/C go ahead and do it. Not really, it takes an A/C mechanic many years of schools and OJT to install and service heat pumps and to be certified by the manufactures. Good Luck what ever you do.
Maybe I'm missing something here, but I'm in the middle of my first split system DIY and it's a HP. I need to run liquid and suction lines, 24VAC and 240VAC, all of which seems like the same things I'd be doing if it were simple A/C, just with more wires on the 24V side. I also need to elevate the OD unit for drainage and snow clearance.
Aside from the W2 wire and O/B wire and programming the thermostat for two stage heating it didn't seem different to me. What am I missing? (I did need help from this forum on the W2 wire, mainly because I looked at a vendor wiring diagram that disagreed with Honeywell and Goodman's wiring instructions)
its not just a 2 stage heating unit.... its a 2 heat 1 cool heat pump system. More low voltage wiring and setup in the thermostat.....that is really the main difference... troubleshooting a problem can be harder for some that don't really grasp how a HP system operates.