OP - I think we are kindred spirits. I still LOVE my Intellimouse and I'm fondling it right now. Well not RIGHT now, I'm typing right now. But I'll be fondling my mouse here in a second or two. I got this mouse "used" roughly 7 years ago from a friend who was trashing an old computer. I know the date pretty clearly as it was just before I put together my first PCLOS box and I plugged that sucker into it and it has not left my desk yet. How can anyone live without Backward and Forward buttons on the sides of their mouse? How barbaric!! It's old, it needs a bath, but it still works great! Hmmm, that last statement applies to both my mouse and ME.
The outside of that mouse cleans up beautifully with a little denatured alcohol on a Bounty paper towel. Not much is needed, just cover the top of the bottle with the towel and tip it momentarily to make a wet spot.
The mouse comes apart rather easily by prying the 4 slide pads off, exposing four small Phillips head screws. It takes a little gentle prying and twisting after that to get around the button retainers, but with the cover removed you can get at the wheel mechanism. The biggest problem there is hair (your own, and any pets you may have) that gets in through the wheel slot. It tends to build up around the wheel axle, collect dirt, bind the wheel, and block the sensor that reads movement using a series of slots as the wheel turns. A straight pin helps to untangle that mess. Once gone, more alcohol on the paper towel, and some Q-tip swabs, does the rest, and it looks new inside and out.
The slide pads can usually be replaced using just the residual glue from the original assembly. If you clean the mouse fairly regularly, that glue eventually refuses to hold, but the pads can then be cleaned with alcohol, pressed onto two sided carpet tape, trimmed out with an exacto knife, and pressed back in place. When cleaned inside and out, the mouse looks, feels, and performs, like it's brand new, fresh out of the box.
I bought this set of small diameter, long reach, magnetic tipped, screwdrivers, for just such operations. I've never used the flat tip drivers, except as the pry bars for the above operation, but the Philips head ones have been used extensively.
$6.23 for the set, on the "Clearance" table of a local major retail outlet. I can't remember which one, because these were also purchased in the late '90s.