You can get pretty vigorous cleaning PCBs without causing damage (remove all socketed chips, wash in sink and rinse, rinse, RINSE then dab dry and leave somewhere like an airing cupboard till it's definitely dry) but given the fault message you've got it may not be worth doing.
I'd suggest opening a thread in Tech forum and including some pictures of the fault and if possible the garbled game screen. Also power up the cab without a cartridge inserted and see if you get the cross-hatch screen. There are a number of fixable causes (as well as unfixable ones unfortunately
) so it may be possible to get it working again.
But you're much better off posting a specific topic in the Tech section as you'll get more people reading it, so more chances of getting help.
cheers
tim