easiest thing to do is get a repair disc off ebay for a fiver inc P&P.
There are quite alot of steps you would not think about doing, eg the 'nostrils' have to come out to access some bits and its a fiddle trying to keep the aircon rad supported when trying to with draw the water rad so the disc is proabably the best option, and then you have it for the next thing to go wrong
HTH