Many, many thanks to all for the replies. One correction, I'm not military, though my original post did seem to imply that. "Deploy" is in our company lexicon though the less ambiguous term would be "transferred." My apologies for implying that.
That said, SUCCESS! I mailed my goodwill letter to Sallie Mae's PA address and mentioned that I wanted to do new business with them, which is true. I also included a copy of the acceptance letter to the Master's program that I'll be attending as evidence that I'm not BSing them. Much to my surprise, they obliged! All told it was 1 week since I sent my snail-mail letter form Germany to when I heard back form them via e-mail. Not bad at all. Good on ya Sallie Mae!
Those 90 days late payments one four separate loans were the last recent (under two years) blemishes on my credit report. Like many here, I've turned a new leaf when it comes to credit and I'll be responsible from here on out.
Good luck to everyone else who's working with SM.
Cheers,
DL
my FICO - 06/02/2008: EQ 727, EX 725, TU 665
TC FAKO - 06/14/2008: EQ 680, EX 727, TU 720