I purchased a Lincoln Weldpak 100 used and it came with a tank and regulator. Do I need a gas solenoid? Or is it unecessary to run a gas setup?

The MIG conversion kit also comes with a wire liner. What is this and do I need it? I'm not sure if hte previous owner installed it.

I dont want to fork out 100 dollars for the conversion kit since I have most of what I need already.