When you download the firmware, also download the instructions. They are pretty straightforward. I have never had a problem with an upgrade either on my H3D or V96C before that. If you don't have a current version of Phocus, I would upgrade that first.
The chances of needing to send it in for service are pretty slim. If you are still uncertain, why not call your dealer, and ask him to talk you through it?
You are also more likely to get good advice on the Hasselblad digital forum which is restricted to Hasselblad owners.