that would be fine and dandy if it had hydraulic lifters! the engine is sorta like the toyota that uses a disk inside a bucket except with nissan, the whole bucket has to be changed which requires the cams to be removed, toyota has a special tool to depress the valve so the disk can be swapped for proper size.
the rattle you hear is connecting rod rattle cause by no oil cushion between rod and crank journal. it could be the oil filter is allowing drain-back or the galleries are bleeding out so the pump must first fill them before oil can reach bearing.