Hi and welcome to the wonderful world of VMware virtualization
1) The hostname listed was created automatically. It is "localhost.XXXXXXX.com". The XXXXXX.com is our organization domain name. When one logs into the network we see our domain name in the network login as a setting. I am guessing that one of two things happened...ESXi installer picked up XXXXXX.com from our network or from some kind of other virtualization that is already installed elsewhere on our network. This used server is in a different department and I desire a stand alone server.
You can easily change the hostname of your ESXi host by logging into the console (called the DCUI) and going to the Management Network portion. There you can set a new static IP and hostname including domain.
2) When I look at changing the hostname through the client I find how to's that tell me to Click on EXSI host > Configuration tab. I cannot find Configuration tab anywhere. I am connected using the web browser client.
These instructions apply to vCenter Server, which you aren't using.
3) I see information on this page regarding placing the server in maintenance mode if I am part of a cluster. I do not see any information anywhere that would indicate that this is part of a cluster. Is it possible that when installing ESXi the installation software searches and finds any clusters on our network and automatically joins them? As I stated above, I do not know if our network has any other VMWare servers running. It is very likely that there is though. This needs to be a stand alone server.
If you installed ESXi anew as you stated, then this host is not a member of a cluster and therefore maintenance mode wouldn't really apply. A host must be explicitly added to a cluster.
4) Lastly, when I do an IP scan using the DHCP IP address reported in the web client I get the name of a completely different computer on the network? Hmmmmm?
It's possible the IP address assigned to this ESXi host has an existing DNS record that may have been left behind and not cleaned up. If you have not done so, assign a static IP to the ESXi server. No ESXi host should have a DHCP if you can help it.