Hi Darren,
while it is a good idea to start with something you are familiar with, this one might be too complex as your first game.
When it comes to adapting existing games, you need to make sure you don't get into a copyright problem with the license owner.
To start with a network game as first game is a good way to get frustrated and end with an unfinished project.
But if these lines will not stop you from trying it, I suggest to start with a simple network game based on the workshop.
Add a chat to your game and allow to switch from 3D view to top view using F-keys.
This will take some time and allows you to learn some new tricks on your way to your first game

You should start with a prototype for your game to learn the engine and its possibilities/limitations and to see if it is fun to play your game - which is the main goal for your game - FUN.
Prototype means that you are not going to create the game now, but to develop an understanding of your games key features and how this has to be implemented with the current version of gamestudio.
Btw. which version are you using?
-- slacer