There is further information regarding the electric wiper motor and getting your vacuum motor repaired. Check this link.
Kev also said this.
"I am sure i posted something like, dont put the old white knob on the new wiper shaft, snug up to the chrome bezel or you will not be able to turn it, you see its a two speed setting , as you turn the knob to the right the shaft needs to go in then out, like on a groove, so if you put the white knob too far close to the chrome dash bezel the knob will not turn/move.
I posted this back in 2002!!"
He also said in the thread above that you do not have to use the black knob that comes with the kit. Use the white one and people will not know you have electric wipers until you turn them on.