Did mine last night... You NEED a drip tray as the gearbox oil starts to come out when you unbolt the switch! It does have a metal U-shaped cage around it, and there are two nuts holding that on after you've unplugged the cable. Then there are two Torx screws to undo and this is where the fun begins.
Take them out and pull the switch from the gearbox. Halfway down the moving part of the switch there is a short roll pin holding the shaft together. Push the old one out whilst its' still in the car and detach the switch. Then simply fit the new switch and push the pin back into place. This is far easier to do that getting the whole shaft out of the gearbox.
When it's all back together put the lost gearbox oil back in via the filling plug hole.
Paul
May 2007