Great advice!
I found that plastic Gap Openers are very good for opening these units up. These Gap Openers are small plastic blades that may be used to prise casings apart without damage, they often come free with equipment such as car dashboard mountings, or can be bought cheaply on the internet, often as part of an "Ipod Opening Toolkit".
When it comes to cleanint the circuit board, I've used a good quality eraser with excellent results. Just make sure you keep the eraser clean throughout the exercise and be sure to blow/vacuum any any eraser particles off the circuit board before reassembly.