I think you could do all the drywalling yourself, but I think I'd leave the bedroom doors to a pro. The bathroom sink you could probably do, depending on what kind of sink it is.
Drywalling is made easy by the fact that there is self adhesive fiberglass mesh drywall joint tape. I use this tape exclusively, and find that it works great. One of the biggest problems new DIY'ers have is taping drywall joints, but self adhesive fiberglass mesh tape makes it a no-brainer. Some people claim that paper tape is stronger. My response to that is: "maybe yes, maybe no, but the bottom line is that you shouldn't be relying on that small difference to keep your drywall joints from cracking, and using the fiberglass mesh tape results in those joints being done as well as they can be using fiberglass mesh tape, even for newbies".
Also, when you're doing drywall butt joints, you can use a "curved trowel", available at any decent hardware store. A curved trowel look like an ordinary plastering trowel until you set it on a table top or sight along it's edge. You'll find that a curved trowel has a bend to it that causes it to arch up about 1/8 of an inch in the middle. Since you hold the trowel at a comfortable angle to the wall when using it, a curved trowel allows you to spread a perfectly symmetrical mound of joint compound, about 1/16 of an inch in thickness in the middle, over a butt joint where you don't have a contoured edge on each side of the joint to bury the tape in.
That shallow mound of joint compound is plenty thick enough to cover over a layer of tape, but it's not nearly thick enough to cast a "shadow", or otherwise make it's presence known, even with ceiling mounted light fixtures.
So, with the use of fiberglass mesh tape and a curved trowel, you shouldn't have too much problem with the drywalling.
(I've been plastering for over 22 years, and there are a lot more tricks you need to know to get good results, but none of them are hard to learn.)
You should always do your flooring last. That's because there's a better than even chance that you're going to make a mess of the floor doing the drywalling and painting. You don't want to make a mess of a newly renovated hardwood floor.