Check the CPU card - if components look corrosed/damaged, I wouldn't even attempt to fire it up. Don't use tap water (or even a toothbrush!) to clean electronic components. Something like contact cleaning solvent/spray, or isopropyl alcohol would be much better.

And yes, the Cube CPU runs @ 100mhz bus same as in a Sawtooth motherboard, so it is interchangable (unlike if you put the same CPUs in a 133Mhz G3 like a DA where you would need to adjust the multiplier on the card itself)