Cacao Nibs

I am going to add some cacao nibs to a stout for a bit. Do they need to be soaked in alcohol to sterilize them?

Is there any specific process that I should use to add them (i.e. grind them), or should I just rack on top of them in the secondary?

How many oz's should I use for a pronounced chocolate flavor in a 5 gal dark stout batch, and how long should I let them sit?

Thanks.

I rack 2 ounces of Nibs straight into the secondary fermenter.

I used 8 ounces in an imperial stout, and it's definately noticeable (you could probably get away with half the amount). Here is what I did. Ground them up slightly in a coffee grinder, roasted in a 350 oven for about 30 min just to ensure they were sanitized, then put in secondary. Since this was an imperial stout they were there for over a month.

For less of a chocolate flavor a couple weeks should be fine.