With ESXi the days for partition management have gone, as RParker rightly says there is no access to other partitions and what is left of the "Management Console" is now a true virtual machine hosted on the local storage.
now that you have the disk geomotry of the old host, just smartstart it create your RAID 5 + one spare and install ESXi from the smartstart. it really is that simple to install.
the fun comes in configuring it 