Chalky,
I had a look at some of these on ebay (some good closeup photos there). Am I right in thinking that the S2 has the shutter in the camera body and not the lens? If so, it makes the lens simpler and safer to take apart. From what I can see--not having tinkered with this specific lens--it looks pretty simple. The rear elements seem to be held in place with a couple of retaining rings that have the slots cut into them for removal with a spanner wrench. The front retaining ring doesn't have the slots--to remove it you'd need one of those rubber things that Micro-tools sells for the purpose. (Or, if you feel adventurous and have VERY steady hands, you can drill two small holes directly opposite each other in the ring face and use the pointed ends of your spanner wrench to screw the retaining ring out.) But once you've got the affected element out it should be easy enough to clean the fungus off. If, as Paul says, the fungus has etched itself into the lens coating you can't fix the damage without re-coating the lens. In any case, you needn't mess with the aperture mechanism, greatly reducing the likelihood of doing any mechanical damage in the process of lens element removal.
