How to restore the ESXI 5.5 preloaded image to the Dell server

Hi,

I purchased a dell R430 preloaded with ESXI 5.5 U2  to the redundant SSD card.

In the event the ESXI got corrupted or in the situation i need to put back the preloaded image, what are the steps?  I understand that I can download the ISO from the Dell website but is there steps on how to reinstall that?

If I have data in the datastore that is not corrupted, can the newly installed ESXI able to remount the datastore and see the VMs?

Thanks.