paint bedrooms - how tough is it ?

I have 3-4 bedrooms to paint, wondering if I can do it myself or do I have to hire a contractor? How tough is it? We will do it before we move in, so there won't be any furniture in the rooms, but I would need to keep the carpet, closet doors, windows clean ... Should I remove the closet doors first? What do I need to do with the ceiling? I am not planning to paint the ceiling, so should I just use some tape to mask the edge of the ceiling and do not need to bother with covering the whole ceiling?

Should I use a sprayer rather than a brush for this kind of large spaces/walls?

Any information would be appreciated! Thanks!