Barring a small miracle, Robs workload will be a little lighter. I likely won't be ready for this deadline
That's unfortunate. Sounds like the new role has you pretty much slammed.
I am just going to go on record as saying that i'm not turning any challenges in. I have no idea on what basis to challenge any of these ratings and how to prove them, so it's better not to invest time and embarrass myself.
That's also unfortunate. There's no risk of embarrassment, though: a) this is all among friends, and b) in the case of many ratings, we don't know any more than you do about how they were arrived at (those sourced from other leagues' files).
So when it comes to making challenges, it simply comes down to looking at your roster, picturing the player and what you know they can do in the NHL, and seeing whether the ratings seem to be a reasonable representation. If something seems off, then you do a little research, looking at how other players in the league are rated (which is why having the ratings list as an excel sheet is so useful - you can sort it any number of ways).
You also look at scouting reports of the player, and at their career performance (with a focus on the past three years of NHL experience where possible) to see whether there is supporting evidence to suggest why the player should be rated differently. So you don't necessarily need to know the formula by which is was calculated - indeed, the formula itself may be the problem with why a given player's rating is out of whack -- statistical anomalies can have a surprising impact.
One suggestion: don't get too hung up on the OV rating (except for goalies) - it's seldom useful in determining a player's actual value to a team on the ice. Focus on the key stats that relate to the role you expect that player to have on your team - those are the ones you care about.
As an example, I've put my submission (along with a supporting chart), in the YahooGroups folder, showing a few different approaches and levels of detail:
http://sports.groups.yahoo.com/group/hfnhl/files/2010-2011%20HFNHL%20Ratings/
I'm not particularly recommending any of these approaches - I have no idea whether any will be successful (and no doubt some of you out there can see hole sin my arguments!) - but thought it might help new GMs to have some context to compare to.