service
1. At what mileage should i take my car into the dealer for the regular inspection. right now i have about 10k.

oil filter
1. How often should i replace the oil filter? every oil change?
2. Is there a special oem oil filter for the s2000? or do all honda's use the same oil filter?
3. Does anyone know price for oem honda filter?

 

Service: Bring it in every 15k miles if you generally don't know what you need done. They'll check it out and replace things that need replacing (brake fluid, differential fluid, tranny fluid, greasing joints, change oil, replace spark plugs, replace fuel filter, etc).

Oil filters will (should) be changed with every oil change.

An OEM honda filter should be around 5 bucks, although don't quote me on that, it's been a while since I bought one. Any major oil change place should be able to find you an oil filter that works. There's not too much difference in filters (as far as I know).