Hi Jarlath!
You can find instructions and SW version 3.0 C on Ketron page under Software menu (if you prefere 3.0 B, I can send it to you).
Don't forget to save Programs, Registrations and the User files before you install new version.
On Ketron page there's also a SD1Plus SW so you can always restore the original setup.
It would be nice if AJ could comment installation of 3.0 SW on SD1Plus just in case there is something that should be considered (I made upgrades and downgrades on SD1 keyboard only)
Best regards,
Luka