I wouldn't advise boiling the nibs.
Some use it in the mash, but I think it gets lost in there. Boiled away and fermented away.
Most craft brewery places will instead age the beer on a bed of nibs. I use around 6 ounces of crushed nibs in secondary. I would normally use them in primary after fermentation, but I find that racking on to them, works out better in terms of chocolate flavor and aroma.
I'd also suggest using 1-2 vanilla beans. It will lend the aroma of a creamier chocolate taste and aroma to the beer. Works fine without it, but if you want to go big, then this helps!
I soak my nibs in some bourbon for a couple days/weeks, whatever time you have. Discard the bourbon if ya don't want it in the beer. I add it, what little I use gets lost in there anyways, and it's packed full of flavor.