Hi DK
If it is your bearings at top of handlebars this is your head bearings. I would replace fairly quickly. Could cause an accident. You will need a manual and some knowledge of bikes.
If I remember correctly it has a shock on the front which is fairly easy to take off. Not sure if worth taking apart just buy replacement, or you could get a can of WD40 and srpay around it (DONOT SPRAY ON OR NEAR YOUR BRAKES) and then bounce up and down to see if this makes a differance? If you are lucky it may just be a bit siezed up and this will free it.
good luck
BB, June 2009