I would recommend talking to your rep - mine set up a webex with me and went through the upgrade. That way they are on had if anything goes sideways. They also have a checklist of pre upgrade things to help make the process less painful.
We purchased onsite tech time. It wasn't cheap but worth every penny. Our Migration was very bumpy and we could not have completed it without help. Lots of odd errors from the installer, things we would have had no way of resolving on our own.