Patching Dell ESXi Servers with Custom Dell Images

Looking for some guidance regarding patch upgrades.

I have an R710 and some much newer machines running 6.5 I'd like to patch due to the recent security vulnerability VMSA-2018-0027

1. The 710 is still running 6.0 - is there a smooth way to get this up to the latest 6.5 patch without losing data?
2. The Dell VMware repository doesn't work.
3. Does vCenter need to be updated, too?
4. All of my machines are 6.5 (except the 1), I do not appear to have Update Manager.

I did a test run (6.5 -> 6.5 patch) via CLI on my homelab and the upgrade went smoothly.. However, my homelab doesn't run the custom Dell image. (I used the VMware depot)

The repos for Dell appear to be broken.  I can visit them direct and they're fine, but once I run:

or

it simply doesn't work.

A rep on Dell's forum says using the VMware depot is OK, but has anyone tried this?  Ideally, I'd like to not lose my networking or config, otherwise I'd flash an ISO.