Mark,
The reason it's not covered is that it is so simple, albeit labour intensive!
It screws into the back of the speedo gauge and screws into a drive on the gearbox.
Follow the run of the original cable thro' the bulkhead and avoid any sharp turns.
Don't be tempted to add any lubrication (oil or grease) as this could adversly affect (or knacker, as we say in the trade) the gauge readings.
Regards, John.