DIY Swap packaged unit

I am looking at swapping out my AC by myself. The quotes at 8-9k are just out of my budget at the moment. After looking at it the actual job doesn't look like its that intensive. I really can not find much information regarding a packaged unit swap online. I need help to know what am i missing? it can't be that easy can it? Disposal will be a hassle but at the end of the day nothing more than a small fee and a hassle.

I am an engineer and deal with wiring diagrams everyday so I am not afraid of wiring issues I might encounter. I will be replacing with a unit of the same size. I would like to switch from propane heat to a heat pump system which will be supplemented by my outdoor wood furnace.