I see that you are wanting to changed your Slingbox 500 for a Slingbox M2, this process does require you to be within the same network to complete the setup. I will be posting some links below that will elaborate more on the Slingbox M2 setup.
- Getting started with your Slingbox M1 or Slingbox M2
- Setting up your Slingbox M1/M2 using Slingplayer for Desktop
Sling Media Support Team