secure Esxi 5 internet server?

Hello,

i plan to operate a esxi 5 test environment for learning in a data center with a fix internet connection.

Since i work primarily with MS windows, i am doing myself a little difficult to secure the esxi 5 server.

For this, i would have some questions for the community.

1.)   1.) The SSH Port is disable by default. Is it advisable to integrate a private/public key encryption? I think the ssh port is a primary attack target.

2.)   2.) The ESXi 5 server creates a invalid ssl certificate at the first installation. Is it advisable to install a vaild certificate as a prevention for a man in the middle attacks?

3.)   3.) Are there any other services to secure on the esxi 5 server for a direct internet connection?

The primary access to the esxi server should be via the vsphere client.

Thanks.

Kr99