The loom is quite straight forward, but it does however interact with the ECU, (So it auto powers off etc) I don't see why you would want to change the screen.

I presume you are going to be fitting the "Black Oak" engine management from the ST, in the conversion, if so you will just have to connect the screen connections to this (Once you have found out the pins)

As it must have been an option on the ST?

Martin