p-Class iLO firmware and bootblock update

[PDP-Fan]

There is an advisory from HP around saying that it is very important to upgrade p-Class iLO firmware and bootblock in case the revision is lower than 1.89.
Ignoring this can cause your p blade to fail completely in case of a power outage or cold boot. Especially after a board replace it is important to upgrade before you shut down the blade for the first time.

Question:
iLO firmware upgrade is easy with the firmware maintenance CD....
But how do you upgrade the iLO bootblock???

HP says that you have to call a HP technician for that but I want to do it by myself. I know there is a switch inside the blade to enable iLO bootblock upgrade... but what comes next?

In case you have a lower firmware there is not much time for experiments. If you have to switch the blade off, it will possibly newer start again. Therefore I want to be sure about how to proceed.

Christian