Grub legacy or Grub 2 in 11.3

Or let openSUSE install grub and if it takes over you can add an entry for Ubuntu
Once SUSE is installed, use the Ubuntu CD to re-install grub 2

I think he meant to replace Ubuntu with openSUSE, not have them both together…

Sorry I misunderstood.
So if you just install on to the Ub* partition - I bet your boot flag is on the extended, leave it that way. And all will be fine.