Firstly the lines you're talking about for power steering is an auto trams cooler built into the bottom tank. If yours is manual don't worry about them.
Secondly, DANG! That pipe is nasty! No wonder you radiator was stuffed! Your cooling system and block needs some serious flushing (packed full of rust, scale and debris). I dare say u did t have any coolant in there at all. Get yourself a good coolant (antifreeze/antiboil is not a complete coolant). I would replace that whole assembly and fill the system up with just water and some radiator flush, run the car up to temp for 20 mins with the heater on. Then drain that shit out, replace your thermostat and put 33-50% coolant to water ratio and ya set (unless I get premix which is already around this ratio). AFAIK nissans coolant change intervals are every 40k. When was your water pump last changed cos I hope it doesn't look like that pipe haha