Default [Q] Updating Sprint Samsung Ativ S Neo to Microsoft's direct GDR3 download

I've looked through the threads on updating the Ativ S Neo to GDR3, and I really want to make sure I properly update my phone to GDR3 from Microsoft, not from Samsung, so that I can still do the interop-unlock.

What do I need to do to get the Microsoft GDR3 update? I know that Sprint's already pushed the Samsung update, so how can I ensure that I'm getting GDR3 directly from Microsoft?

Thanks!

ETA:

It turns out my fears were for nothing - I thought Sprint had already pushed GDR3, but it appears they haven't. I did the developer unlock and installed the preview for developers app, and the only updates that came through were from Microsoft directly.