Need urgent tips on retrofitting FFB

Hello have bought me a FFB for retrofitting, since my lock mechanism no longer works. (V8 3.6l)
Now I got such a great schematic with installation instructions which unfortunately does not bring me much.
Is everything too confused for an anti-electrician.
Where can I find the appropriate terminals, cables, etc. to which I connect the control unit of the FFB??? Where is the ECU placed??? It is described to be cut through the wires ??
Are the cables to be connected all in the driver's door??
Cover, etc. I've been putting down
Who can give me "assistance"?
As it is described, it can't be so difficult, but if you have never built such a part into it before ....
FFB is offered by Ebay and by Baunsal
Thank you for your help

Greeting Flo