Is it leaking? if not, it may just need to be flushed. Trace the pipes leading to the matrix and connect them to a hose or something.
I recommend you buy a haynes manual. If you are serious about working on your car it will be invaluable. There are several tricky stages to removing the matrix and I don't fancy typing several pages of instructions.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.