Thanks for all the comments!
We used yellow poly line. I buried it around 20" deep and then covered it with about 4" of soil. I then laid an insulated copper wire in the trench with it coming up at the ends for future locates. The idea on burying it slightly higher is that if you get carried away digging on top of it you will hit the "locate" wire first and realize what you're about to dig into...
One of those tooth bars is on my wish list. I should of bought one over a year ago when I started working on my new property!
My main priority now is to build a ripper tooth or a bracket to mount a boxblade ripper to the BH. I have a few big stumps to take out so I can build a metal building to store my tractor, implements, truck, and project car. That way my attached garage doesn't get too crowded!