OK that's definitely rod knock, and the vid is a pretty bad case. Not the worst thing I've seen (a symphony of 4x rod knock is awesome), but I wouldn't expect to reuse that crank (and have it last). Tear it down and have a look. Worst case is the crank is done and you spend an afternoon at LKQ Cophers digging one out of a SER. A full set of bearings at Nissan is $100. Not a lot of money involved, but lots of time.

You can technically change the front cover with the head on, but it's a super duper pain in the ass and you'll probably destroy the front of the gasket and have a major oil leak. Been there, redid that. The problem is that the cover has to be installed parallel to the front of the block because the oil drive collar won't allow you to tilt it. There are also locating pins that interface the cover as well. If you do wind up changing the crank, you can probably make it work, though. With the crank out, slide the cover on the drive gear. Then you can position the combo without a problem. You might have to pull/reinstall the pins on the front of the block, too.