The other issue that came up on my first outing with my BM M4 (besides the noise) was that I had to adjust for very excessive windage. I understand this is a common problem, and I know that BM will fix it for free, but being a newb, I don't know exactly how to go about it.

Could someone outline the whole procedure for me? (packaging, warranty issues, etc.)  I've never mailed anthing quite like it so I want to get it right.  

BTW: I'm fairly sure the barrel is mis-indexed, but It would be nice to know if there is an easy way to tell for sure.

First, you could call them. Their customer service is top notch.

When I had to send one in, I just boxed up my upper, minus the bolt assembly and charging handle, and sent it to them. Enclose with it a letter stating that you think the barrel might need re indexing and what its doing to make you think that. Pretty simple. From the day I sent mine out until the day it cam back was only 13 days.