My Elite was accepted! $200 for "good".
Considering I had most of the original packaging but the box and controller were a little beat up, and considering I've gotten many hundreds of hours of gameplay out of the 360 in the 4 years I've had it... I couldn't risk attempting it as "like new".
Now, it's time to get a new slim with that credit. I'll have to get another hard drive, but I can use my 16gb of flash memory all my stuff is stored on for now.