Here you go. The standard return line kit is what you need. You can also get the exact same kit from typ4 / Russ, probably for a better price. I originally used a kit from O'Reilly's when I had my IP and injectors replaced, but my IP didn't want to run out of the box so some "extra steps" had to be performed, which quickly put an end to that return kit. I drove it for a month with it pouring diesel all over itself (and amazingly, despite the massive leaks, I never once had air intrusion symptoms
), finally put one of Russ's kits on it and it's been dry ever since.
As for lube for the o-rings, you'll hear 100 different suggestions on what to use. Vaseline, bearing grease, lithium grease, ATF, motor oil, KY Jelly, it all works. When I did mine I used clean motor oil and had no problems, but I can see why a thick grease would be preferable. Just make sure your caps are 100% seated, if you don't feel them pop in to place then chances are it's not fully seated. I had some trouble seating the caps by hand, so I put an open-ended wrench over the cap and gave it a love tap from another wrench and that did the trick.