Painting interior is pretty doable - there are a lot of good tips in this thread (and probally others posted on ATOT). I would seriously give it a try before going to a contractor.
Prep work and clean up is probally 80% of the work. If your prep right all you need to do is paint, and painting is not difficult. Mask off everything, make sure you throw down tarps (most likely cheap plastic and low mil drop cloths) and then go at it. Keep a wet edge when you paint and your job will look nice.
Painting 1400 Square feet of wall (unless you have funky walls) won't be too difficult. Just get a handle on edging and you will be fine. I have only used a sprayer indoors once (a real sprayer, Graco rig), Most of the time indoors i just use the good old fashioned rollers and brush. Once again.. if you do the prep, you will just have to roll for a little bit, edge for a little bit, then clean up.
I prefer to use Kelly-Moore paints, Paint quality does matter, but unless you're using the water colors from some cheapo place (walmart...) you'll probally be fine. Painting is almost intuitive.
Painting Exterior is something i'd want a full time painter to do, but with an interior job - It's not very difficult. My parents repainted their entire house with paint and prep stuff i picked up for them, and they had no problems. I'm sure you can manage it too 🙂
Checklist
1) Paint - select the right paint, most likely interior flat, stir sticks, etc
2) Drop Cloths
3) Tape (Get the blue painters tape as it will be least likely to damage the surface it is applied to. Pull slowly, because if you pull fast it will tear at the surface regardless)
4) Roller Frames
5) Roller Covers
6) Roller Extension - if you have tall walls.. also you probally have one at home as this is usually just a broom/brush handle.
7) Brushes (get a nice good brush. Though they may run you upwards of 20-30, it will more then likely be a one time investment if you take care of it)
8) Roller Trays, Liners, etc
9) Cloths to get dirty
10) cleaners
Just map out what you need, what you need to move, cover with drop clothes, tape off, remove from the walls, etc - once you have the parameters of the job, it'll seem pretty simple (because it is)
If you have a buddy whose ever painted, ask him to go with you and help you pick out what you need. Good painting and pics of the place when you're done. 🙂