Dish soap and water with a little bit of rubbing alcohol mixed in. I've never scrubbed the lettering off any of my Yamaha gear, and I have much of it including CR-420/620/820 which I've cleaned extensively. Obviously, use common sense, don't get after it with steel wool or anything crazy like that. But the lettering on Yamaha gear is pretty good, you're not likely to accidentally rub it off.
Taking off the faceplate will make washing it so much easier. It's not too difficult. The paddle knobs and tuning knob are held on by little set screws, you'll need a small hex wrench. The holes for the screws on the paddle knobs are on the bottom. The tuning knob is a little trickier, once you have the cabinet off you look in through the side and you should be able to see the identations for the set screws on the backside of the knob. It sounds more complicated than it is, trust me. Once you have the paddles and the tuning knob off there is a series of small screws on the top and bottom. 3 of each I think. Remove those and the faceplate should pull right off.