the cage like cylinder is the collapsing mechanism. you should be able
to remove the nut with a 1/2 inch drive socket with an extension. there
should be no direct obstruction, there are no rivets or anyting else to
remove. Look in the Porsche service manual, Haynes is pretty worthless.
Travis at Renbay has the odometer gear if memory serves. bulbs can be
replaced from under the dash, you don't need to pull cluster. Be
careful changing the odometer gear, it's easy to damage the speedo.
I've done this exact repair on an 85, an 86, and an 87, and in no case
did I need to remove parts of the steering wheel. It is easier to get
the cluster out with the steering wheel removed, but it is possible to
get it out without removing the wheel. Non-cancelling turn signal is
VERY hard to fix