Service Bulletin work

This depends on several items. Are you a mechanic, have you had any Rotax training, what type of certificate does the aircraft have will depend on who can work on it. Some bulletins mat be easy and some a trained Rotax tech should do it..Sometimes parts are required and Rotax will help and other times it may only be an inspection.

Everything rides on the type of bulletin, its wording and what is needed to be done.

I'm not certified as a mechanic. But I have done mechanical work on small and large engines over the past 20 years. The plane is an experimental. The bulletin requires new floats for the carburetors. 

This information is found in the SB that you are looking into. 

Take for example this SB - https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912-075.pdf

Exchange of carburetor support springs on ROTAX® Engine Type 912 and 914 (Series)

1.7) Labor time. A labor credit will be provided for work performed by a technician with a current applicable iRMT rating.

Work on EASA certified parts might affect the EASA Form 1 and does require appropriate documentation by authorized persons. Repairs must be entered into the engine logbook and also do apply for the EASA Form 1.

All measures must be implemented and confirmed by at least one of the following persons or organizations: - ROTAX® - Airworthiness representatives - ROTAX® - Authorized Distributors or their independent Service Centers - Persons approved by the respective Aviation Authorities - Persons with approved qualifications for the corresponding engine types. Only authorized persons (iRMT, Level Line Maintenance) are entitled to carry out this work - Persons with type-specific training

Price and availability will be provided on request by ROTAX® Authorized Distributors or their independent Service Centers.

Thanks!

In the USA, only the FAA determines who is approved (certificated) to do maintenance or inspections on aircraft, not manufacturers (regardless of the "wording" in the SB.)  Having said that, manufacturers' training in the maintenance and inspections of their engines is recommended.