You can clean it with soap and water, but you'd need to dry and regrease all the bearings (headset and wheels) afterward to ensure that they don't rust. Better yet, just use a wet rag to clean off your deck being careful to not get water in the headset or wheel bearings.
If your current scooter has a threaded fork, you don't want to keep using that fork. You'll want to upgrade to a threadless fork, threadless headset, and compression system on your scooter. If your current MGP fork is threadless, then you'll probably need to stick with MGP decks since they run shorter headtubes and, therefore, shorter forks.