L.A.D. Specialties
I’ve been their customer for decades and they do excellent Rotax work. They’re in Bridgeview, IL, so you could drive there, otherwise the close distance will cut down on the shipping charges.
ladspec.com
It is a pretty simple fix, but you do need to split the cases. Any Rotax Service Center should be able to do it and tell you how much it will cost before you ship your motor to them. Sounds like L.A.D. is close to you and that can save you money and time.