Was your donk already mated to the auto when you got it or have you got your CA and then sourced the auto separately?
If they came together it should be pretty straight forward. All the sensors you mention are all very important. Especially coolant temp, cam, speed sensor etc as they all control the fuel delivery and spark timing.
You can use either the dash out of the Silvia or you can get electrical replacement gauges (Autometer, etc). With a coupe dash (3 round dials) you can pretty much just plonk a 3 3/8" gauge straight in the hole. Some people like to mount them from behind for a more factory look.
If it all gets too hard there are a few places around that will do a full wiring loom for you to match the recipient vehicle.
Good luck!