first off congrats on the purchase
the cleaning products comes down to preference on a lot of things, check out the section on it.
petrol - the higher octane stuff is favoured i believe but regular shouldnt do any harm (i may be wrong)
stubby, search for an s2000 one, they are common and good
i cant remember what that button does in the middle but there was a thread about it not long ago
plenty aftermarket sat navs and car pc's been done and some for sale, use the search
bluetooth adaptors - :pmr35lee: i think he had some and i think he had a steering wheel with the controls for sale but i wouldnt have a clue how to wire it up, he should know if you pm him though
oh, and one last thing...
search is your friend...