I would guess that the existing temperature sender and wiring may work with the new gauge, but you may need to fit a sender to match the gauge. The pressure light will work off your exixting sender and wiring, but you will need a matching pressure sender.
I too am going down this route I did buy from a company new gauges and sender units they were resonable priced to.
Sewell of leeds
0113 243 5101
The senders have a thread size of M14 x 1.5
the oil temp one for the 912 I ordered to match the gauge was a
323.801/004/030K
Now with this gauge do you just need to find the correct sender unit or do they have to match in some way. I would have though just the correct temp range. Which the above number is.
As for fitting I was going to plum in on the connector under the oil filter I can get the oil temp there but can't remember if I can add in a oil pressure sender? as well.
Oh also the guy I spoke to was Graham Park nice guy arrived Next Day.