I would definately paint the wall and paint down a good foot below the intended chair rail. This will save you time in cutting in with a brush.
Katy, the project is relatively simple except for one main issue. Can you cut good quality mitre 45 degree cuts for the inside angle corners? If you cannot, then do hire this out. Do all you can then bring in a trim carpenter to do the mitres. Nothing looks worse than a poorly cut corner.
You can do the rest without much trouble.
You need a circular saw or a jig saw, caulking gun, hammer and panel nails, liquid nails, level, paint brush and roller and drop cloths.