"How do service bulletins work? Must the work be done by an authorized Rotax shop? Can I do the work? Do they supply the needed parts? Or do I need to buy them?"
Simple questions but complex answers, as the answer depends on a lot of factors.
"Must the work be done by an authorized Rotax shop? There are really 2 types of SB, normal and ASB or alert service bulletin. An alert is a safety of flight issue and should be addressed as quickly as possible. Rotax does not authorize a shop, that is the function of the distributor or the iSC, independent Service Center that works under a distributor of Rotax Aircraft Engines. The distributor most likely has a network in place to support the engines of workshops and independent Rotax technicians. Rotax spells out what requirements they have for the completion of the buliitian to their standards irrespective of the regulators additional requirements.
"Can I do the work?" is a really difficult one to answer in that yes and no...it all depends. If the aircraft is an experimental, at least in most countries, sure you can. You might not get paid labor for that part of the SB however as Rotax clearly wants you to have training to do such work to the level required for that task. The regulator may also have requirements as to who they approve so you need to understand your situation from a regulator viewpoint. Clearly having approval from the regulator, say A&P or LSRM in the USA with additional training to iRMT is the most desireable.
"Do they supply the needed parts? Or do I need to buy them?" Yes they can supply parts but you might be charged for them. You need to fill in the required information usually to get them and in many cases return old parts as verification you actually did the exchange. In the case of floats I doubt there should be much problem other than filling in the required paperwork, check with your iSC to confirm what is needed in your area.
Cheers.
