Thanks for your replies.
@andyinv I read through your thread and that’s why I am even more motivated right now 
I called my friend who owns the tractor. I got more details. He told me it is autosteer ready but it doesn’t have the antenna and I suppose the GPS receiver and modem neither. So I am wondering if it is really autosteer ready and what does the autosteer ready system include ?
The warnings I got were about sending messages to the canbus on a tractor on which the WAS and the steering valve are not calibrated. I found details about this in the following thread : Massey Ferguson 7700 autosteer ready - Projects - AgOpenGPS
I was told we should take the tractor to the dealer and have him calibrate the steering system. Only then can we send orders to the canbus safely. The risk being to block the steering valves if we keep sending the order to turn left/right when the wheels are already in the max turning angle.