Don't use polish on the screen. You've also got various anti-glare and anti-reflection coatings on the screen and polish will reduce the effect of these. A damp cloth is all I'd take towards any monitor, plasma included. As for the surround, maybe a little bit of polish...
A damp cloth will leave water marks - the best imo is methylated spirit, which clears finger marks and anything else. Been using it for years - no problem. Don't use white spirit though, as this also leaves a deposit on the screen.
Well if you rteally want to spend some money on your screen and you have deposits that will not come off with just a damp cloth, get some RS screen wipes, these are designed for computer monitor screens anti glare and all!
Still think a damp cloth is all you need quite frankly!