Mouse poo can contain potentially-fatal hanta virus, which you can catch by inhaling mouse poo dust.
What to do about it: Get a spray-bottle and fill with a mixture of detergent and water, and spray the mouse poo thoroughly to prevent dust; then wipe it up with paper towels and toss them in the trash.
If you've already vacuumed up the stuff and not gotten sick within a few days, then probably your mouse poo was merely icky rather than dangerous.
Anyway... good find; will be interesting to see what you do with this one to get it fully resurrected.