Just be careful of the fumes. I'd plastic of the water surface at least for the beginning stage of paint drying. Turn off your skimmer or any air/water mixing equipment. I've been paranoid of even the smell of acrylic paint around our tank.
Will I have to sand the wood.? It looks like it has a light gloss coat on it.. I work on paint for an industrial company so I'm really informed on paint stuff I just want to put something safe on my stand and not affect my system..