old fuel lines and brake lines -Replacement Where and How? Tech tips please!

Poly armor line is the stuff with the green coating, its basically a steel line with a plastic coating over it, as long as you don't scratch the coating off it will last a while even in the rust belt, but if the coating gets rubbed off there's no corrosion protection.
Copper nickel line looks like a new penny before it's exposed to the elements.

I've installed probably a thousand feet of this stuff in the past decade working on peoples rot-box daily drivers here in the salt belt, I haven't seen it fail (rot out) yet, the only problem I've had is when replacing a brake hose the steel fittings rust themselves to the line.
Copper nickel is well worth the extra money, you'll never have to replace the hard lines again. Oh and it's super easy to work with, flares easy and bends by hand.