If you have a lens spanner & can get the name plate off cleaning the inner face of the front element should be relatively easy. Iso-propanol or hydrogen peroxide are the best ways of removing the fungus, generally by gentle rubbing via a paper towel. Servicing any deeper or opening the rear of the lens is likely to be a disaster - zooms are complex beasts! Tiny screws as used in lens construction are frequently secured with some sort of thread lock. Gentle application of heat or acetone can release them. I'd try a soldering iron on the screw head first. Acetone can be a real problem if it gets on plastics, but application via a q-tip should do the job as well.. As far as plurals go, the standard in English is to add 'ES' to words ending in 'S' so 'lens' becomes 'lenses' as a plural. It is common to see non english speakers simply removing the s to make it singular but this is incorrect.