Sounds like the timing chain guide is broken and has slipped, thus allowing the slack
in the timing chain. Nissan is very much aware of this problem but has done nothing to help out the owners who’s warranty has expired. I highly recommend NOT supporting Nissan
by not having the vehicle serviced by them.
I also had an oil leak. For me the fix was simple. My leak was caused by a wrong size O-ring within the oil filter housing. This is also another wonderful Nissan Quest feature.
Look it up on the internet.