Sounds fair enough. If you end up getting into it and doing any sort of coverage, do let me know. I'm gonna write the XBA guide for it (though I imagine it'll be just as big of a bitch to cover as video).
For Challenge maps, you NEED to play on "I am death incarnate" (or higher) to register a gold.
From there it's all about scoring and surviving (which can be a little difficult). Kills get you a certain amount of points (400), you get extra for headshots/explosions/marksman (200), and then additional points (200 per kill) for killing enemies in combos.
Basically just work that formula into the situation, and you should be good to go. The challenges can be difficult, but as long as you are good enough to survive them, you shouldn't have much of an issue reaching the needed score.
Obviously they are accessed from the main menu, and unlocked as you progress through the campaign.
Right on! I've been playing all morning and posted my guide a little while ago. I mainly just need information on the Challenge Maps (I haven't touched the two I've unlocked) and some info on pipe head explosions (for the perk). If you have info on those, that'd be great. Then I'm gonna add a little text-based info for the letters and everything should be good to go.