Hi Tony.
Welcome to Pagoda ownership!
I just may be able to help with your headlamp query. Your lenses should be glass, although I believe that plastic aftermarket replacements are available. I noticed 'dullness' in my lights when I bought mine. In addition a fog lamp bulb was not working so I decided to restore both of my headlights. Its a relatively simple process, but you need to take care when removing the lenses which are held to the lamp chassis by small 'U' clips, which can break the glass.
You may find that the issue you have is rusting of the reflectors (see photo's). These can be replaces, available from either MB or sls-hh in Germany, but when I priced up replacements I determined it was cheaper to have them re-silvered (note they are slivered and NOT chromed). You can see how bad mine were, and how good they looked after.
I wrote an article for the MB Club Gazette which details most of the things you need to know, I will find this out for you and scan it in tomorrow.
Regards
Mark
