You can do it one of two ways. Buy the kit from Cajun (~$40) or do some sourcing on your own and save a few bucks. If you self-source, just be sure you get the right fitting (I ordered one from Nissan, a perfect fit) and plan on going to multiple parts stores to find a fuel filter without the check valve. I think, all told, I spent about $20-25 and a couple of hours sourcing time, plus 20min to install it.
I guess there's a third option. You could do nothing and pray it doesn't bite you, then complain about how crap Nissan is when you have to shell out for rear axle seals. But that's not smart.
This type of mod was the first thing we always did to every truck we've ever owned in my family. Used to run the lines up to a t-fitting mounted to the firewall and vent both diffs there, with a nice (chrome) Moroso valve cover breather as the vent cap. This is way easier than all that.