I'd say carry on yourself with what you feel you can and get the bits you know you cannot do checked by your local engineer (not specifically main agent) if you feel the need! You could remove and check the stat yourself, or change it whilst your there, cleaning out the housing etc while your at it.
Your engine should give you warning signs if its got more serious issues that need further investigation. The beauty of a simple, traditional 2 Stroke over the more sophisticated models that would obviously need dealer diagnostics
Peter @ Boatsandoutboards4sale ~ www.BoatsandOutboards4Sale.co.uk
~ 07930 421007