Changing Fuel lines

What do I need to do? I see there are 2 lines visable on my tank. One would be from the sender its self, which I believe the gas travels from to the engine and The second one right above this one, but on the tank that runs along side the other one, but to the Engine bay. What is this for? and Do I need to up grade this one or can I get rid of it?

I want to go to 3/8 fuel line, but I dont know if I will only need metal fuel line or metal and rubber.