Apple iMac 24" Screen issue

you are not alone. its not that hard to clean. really you need the cloth that came with the screen...most people throw it out. and all you do is dab it with a bit of water and gently massage the screen. and it looks as good as new. if you dont still have the cloth use a very silky delicate piece of cloth. if it is underneath the screen (very unlikely) take it back to the shop you baught it for and if it is an apple store then they will most probably clean it for free. 
also do the stains look like the are on the inside or outside? and, do they move at all?
if you took a picture of your screen and posted it on here. i will be able to give you a better idea on how to.. fix ya