I'd demo whatever you're replacing.
Mask whatever is staying.
Prime whatever needs to be primed (cabinet boxes) you may even want to just finish those boxes and get them masked off, as well as any othet trim thats staying.
Then spray the walls out with your first coat.
Use a hand masker and 12 in paper (or bigger if ya want) and run it at the top of your walls around the perimeter of the ceiling. Shoot and backroll (use a "wand" extension several sizes available. I like the 12" , easy to manage-- especially when you get into the bedrooms and closets and such) the ceilings from the scaffold or a step ladder (which might be easier to manage) get an extension pole (I like wooster sherlock frames and poles 5-10' or 6-12' (depending on how tall you are.) And backroll from the ground.2 coats on the ceilings.
Unwrap. Finish (roll em) your walls. You've already got a nice straight line at the top so it'll go fast and easy. Flat ceilings. Eggshell or satin walls. Satin or semi trim.
Buying a used pump is a crap shoot on Craigs list. Ya might want to ask your PAINT STORE (not box store) manager If he knows anyone selling a pump. Maybe a crap shoot too, but a painter will usually take better care of their pump than a home owner. Ya might even consider buying a used one from the local pump repair place (-best bet-ask the PAINT STORE manager who that is and phone #) sometimes you'll get a much better deal on something someone never picked up. And you'll likely get something more dependable which you'll need for the interior as well as the exterior. They'll also happily instruct you on properly using and cleaning out your pump.( I'd use a 515 or 517 tip inside and out on your home btw...). Buy your paint at the PAINT STORE. Sounds like you've got a lot of work. Don't try to cheap out on the finishes or you'll be sorry in a few years when you're repainting OCCUPIED.

Happy painting.