During the warranty period you need to use fluids and parts of the correct specification as stated in the manual. A 30-weight oil with an API doughnut symbol on it is required for this, as is an air filter that meets the OEM spec. The gear oil is not due for replacement until 60K (assuming it was done at 30K). The plugs are also not due for replacement until 60K. The fuel filter is not a required replacement part, it is recommended. Check the manual for the service intervals.