The D60 is a fantastic camera. I've had it for a month and wouldn't trade it for a film camera for anything.
BUT, if you're not going to carry the whole load, ie a laptop in addition to the rest of the gear, I would hesitate to move over to digital for an Africa trip. The images from D60 are incredible, but take up a lot of space, and I wouldn't rely on anything else than a laptop with a cd-burner, because you might find yourself stuck in some far away place with nowhere to transfer your pictures. Also, one great advantage of digital to me, is the ability to see and work on the images immediately, which again means a laptop. Which means more bulk, more fragile equipment, more charging problems, and a lot more costs.
As for a comparison to film. Well, you can print top quality A3 photos from the D60, and even ress them up bigger in Photoshop. If you're not planning on making posters, then it's good enough for most people (actually, with a little processing, you CAN make posters from the D60...).
And as has been said, keep the number of lenses to a minimum on the D60. Other than saving bulk, you save the sensor from being exposed to a dusty environment during lens changes.
Good luck, whatever you choose.