At this point, you have 3 options. #1 is to try the linux based update packages from within Xen, they should work properly. #2 is to use Repository Manager to create a bootable deployment media that you would boot the system to, and the it would automatically update the system to the latest versions of firmwares. The other choice is more complicated and requires the use of the Systems Management Tools and Documentation disc that comes with most servers, and a Server Update Utility 7.x from the support site. I would recommend the RM disc as it is much easier and less downloading.
Rm can be downloaded from this link: www.dell.com/.../DriverDetails
The 2nd video at this site details how to create the bootable iso en.community.dell.com/.../1767.dell-repository-manager.aspx