Hi,
Probably best to post this in the GRC forum but my thoughts are:
It's not an upgrade, it is a migration. Your Basis team will build a complete new stack but you'll need to agree who will do stuff like activate BC sets etc.
There will then be plenty of work for whoever looks after the current GRC system - importing rulesets (if you don't take the standard), FF setup, rebuilding CUP/AR workflows etc (do not migrate CUP).
There is a lot more to it than this, I strongly recommend that you go on the GRC300 course. We are seeing a lot of clients who have had problems with their 10.0 implementations, much of it avoidable if they had attended the course.
Cheers
