How accurate are these upgrade procedures?:

Consultant's Corner: Upgrading to GroupWise 8 - Part 1: ConsoleOne, Schema, SDD | Novell User Communities

We have 2 Domains, 2 POs, 1 GWIA and 3 Webaccess agents. 1 server per PO/Domain. Gwia is on same server as primary Domain. Webaccess is on both domain servers as well as it's own server. I plan to follow these instructions to the "T" so hopefully I will not run into any issues. The only problem I forsee is if I have to roll back, what would be the process to undo schema extensions? Or can I just go back to 7 with the 8 schema extensions in place?