To answer your first question, it's barely worth the time it takes to decide. I often lubricate sticky cables, but sometimes, it takes so much effort that I realize I should have replaced one. Try either, and you'll know soon enough which is the better strategy. Cables are cheap, and oil is cheaper.

Brake cables and housings are pretty much the same as they've been. Housings for shifting have changed, though, so use housings that are designed for shift cables. New shift housings are straight, not wound.