Sue,

Not sure how far you plan to go in eastern Malaysia, but I'd recommend climbing Mount Kinabalu. It's certainly do-able - just take it easy, and you get a great view from the top.

If you do it, then go to Poring Hor Springs afterwards to soak your muscles. You'll need that, believe me.

For getting around in Borneo, the tip is to fly. The flights are dead cheap and beat sitting on a bus for hours.