I've successfully recabled my pair of E2C's. The E500 looks a bit different though, at first sight. I'm at work right now, so I can't really check out the details. Mine opened by simply taking the small blade of a swiss army knife (because it's thin), and sliding it in between the two halves of the shell, all across the line. Don't stick it in too deep, you don't wanna damage the innards. I was lucky Shure didn't go overboard on the glue to keep the parts together, but I noticed the first one went a lot smoother than the second. I'm not sure what kind of glue Shure uses, but you could also try the hairdryer technique to see if it softens up. Don't get that stuff too hot though.
After you're done recabling, glue the halves together with a glue that doesn't condense. So no cyanoacrylate based superglue; you don't want that stuff to condense on your driver diaphraghm.
You might want to check into the possibility of replacing the cables with plugs for detachables while you're at it. I haven't done that on my E2C's, and frankly, I'm regretting it. If I were to recable them again today, I'd order the Shure cable that goes on the SE series, and then hunt for a set of matching plugs at my local electronics components store. If it can't be found, you can always go with a custom cable and just sell the Shure cable.
