Hi Scott,

You may already be planning this, but if not you should definitely hike up to and past the E-Ledges before attempting in the dark. Also, if you have not already done so be sure to review the links to MR advice:
http://www.whitneyzone.com/wz/ubbthreads.php/topics/1867#Post1867

The MR is not a trail, and it is fairly east to lose the route, so preparation is key to success.

Good luck!

John