10 mm. One side is a nut that doesn't turn (welded on the bracket). I suspect that's where you're trying. On the other side is where you want to be. Takes a deep socket and the hex head screw is aways in, coming from the drivers side. Remove the whole bracket.
The tabs can be bent on the aluminum rectangular box and the innards released that way, if you are planning a resolder.
The car runs fine with the cruise control in any state of disassembly (just unplug it), so it's not neccessary to complete the repair in one session.
Pindelski is here:
http://www.pindelski.com/
A GREAT site!