I took my remote apart today for a cleanup due to keybounce problems.
Thought I'd throw this guide together for those of you that want to try the same.
I already had a mobile phone toolkit, these are about £10 from Maplin Electronics (Code QE69E). The only items you actually need are a small phillips screwdriver and the "panel opener", which is the yellow thingy in this box. Failing this, it would be fairly easy to buy a cheap small flatbladed screwdriver and bend the tip at about 30% in a vice.
First step is to open the battery compartment and remove the batteries and the small phillips screw from near the bottom.
The hard bit is next. There are five clips moulded on each side of the remote. Using the photo as a reference, carefully push the panel opener (or modified screwdriver) into the seam in a position near a clip and lever the case slightly apart. You sould be able to work round each clip in turn, releasing it. With care I managed to unclip the case without causing any damage to the plastic.
This is what you end up with ! You can pull the rubber keypad away from the front and blow out any dust (or dog hairs in my case).
The circuit board can be cleaned with a lint free cloth or kitchen tissue and a little Isopropyl Alcohol (NOT Malt Whiskey, it's too precious)
I also ran the cloth over the back of the rubber contacts, but I'm not sure if this is recommended.
Getting it back together is relatively easy. Make sure all the rubber buttons are pushed through the front panel. Carfully line up the two halves and squeeze them back together.
I hope this is of use to somebody. Best of luck. You can email me, or PM JoNk via the Tivo Community forum.