The day after doing this repair; remove the radiator cap again, and check and refill as necessary the coolant level in the radiator with the motor cold and idling . There is often trapped air that will come out of the system, which will cause the coolant level to drop. Only after the air has all come out of the system can the level be trusted in the overflow reservoir. If the level was significantly low, recheck it again on one or more subsequent days; until it stops dropping; or until the source of any additional leaks is discovered and repaired.
You'll have to remove the plate in the back (held on by four bolts) to access the camshaft seals and bypass hose. Take the cam sprockets off first, impact is a must for this (unless you have the crankshaft pulley on still). I'd recommend replacing the bypass (small 90 degree) coolant hose with the Nissan part.
The bypass hose connects to a body where the upper radiator hose connects. There are 2 or 4 bolts holding this said body on to the block... Get the gasket and seal out of it.