Upgrades before Africa:

1) Put on heavy-duty touring tires. Since 700c is uncommon, get GOOD ones like Schwalbe Marathons. As Cyclebum said, learn to boot a tire, learn to sew a tire, bring lots of spare tubes and maybe grab some tire liners.

2) Have a local bike shop check the trueness of the wheels.

3) Make sure the seat is comfortable. If it isn't, ask your local shop if you can test some others until you find one that is comfy.

4) I'm actually going to go on the dissent here and say you DON'T need to upgrade your handlebars, add grips, or bar-ends. Since your bike's geometry is fairly upright, you won't have much weight on your wrists and the current handlebars will be fine. I think there's a knee-jerk "hand positions!" reaction on this forum to flat bars, but that's very low priority in my mind. WAY less important than the wheels and tires.

5) Racks and Panniers- figure it out now so you can make changes.