My poor SONOS CONNECT AMP got wet

Sonos doesn't have an authorized repair network, so it's unlikely that you could send it anywhere to get fixed. You my want to replace it with a Sonos Amp, since they don't sell the CONNECT:AMP anymore.

If the unit was powered while wet, damage can be severe. Note that "wet" pertains to the internal electronics, not the case. It would require at least several days for the internals of CONNECT:AMP to thoroughly dry because of poor air circulation. Powering a still wet unit will complicate the issues. A clean water spill into an un-powered unit is not usually a big deal -- unless one applies power while the unit is still wet. Rain water is not "clean". Soda spills and such are very destructive because they are conductive and residues form acids that will destroy the components over time. In case of flood or soda spill, immediately remove power and, if the unit cannot become any wetter, flush the unit with clear water and have the unit serviced by a pro -- before applying power to test the unit.

I like to do the initial flushing of contaminated gear (soda, coffee, juice) with warm tap water as it is effective and cheap but I follow up with several rinses using distilled water to minimize the internal contamination from the crud in normal (even RO'd) tap water. Under a buck a gallon and cheap insurance.

You can speed the drying process with high volume but low pressure air, a blow dryer set to cool works, reversing a vacuum cleaner is iffy as it tends to blow fine particles deep inside.