You can take it out and clean it with a lint free cloth. Losen the screws that hold the buttons in place slightly and remove the small screws that hold the LCD module and it should be possible to take it out. However, in my experience it's hard to get all the dust out
Also, be careful with the two cables, they're frail.
How on earth did you get dust on the mainboard anyway? It's a closed box after all.