Here is a video of the installation of a Momo Prototipo steering wheel in my 2002 Boxster S. This process would be the same for just about all 996, 986, 993 and pretty much 997's as well. Hope you find it useful !!
The horn contact is part # 96465210400
Electrical pin for steering column 999 652 639 22
The resistor is a generic 3ohm resistor from amazon