Pelican Parts Forums - Towing Hitch Questions...

So, my local Porsche dealership wants approximately $1800 to supply and fit a trailer hitch to my CTT. Looking around the Pelican and Rennlist forums this seems to be consistent with other dealers, but to me it seems excessive for something so simple. Right now I think I have three options:

1) Pony up the $1800 and 'get it done right'.
2) Pay approximately $1100 for the towing hitch kit (which I believe consists of the hitch, control unit to talk to the CTT computer, drive the lights etc. and the wiring back as far as the hitch itself), do the install myself and have Porsche enable the control unit with their PIWIS system.
3) Pay $153.47 on ebay for a curt trailer hitch (Custom Trailer Hitch Products, Custom Receiver Hitch, Heavy Duty Towing, Curt Manufacturing), buy the control unit, wiring etc. from Porsche, install it myself and have Porsche enable the control unit with their PIWIS system.

So, a few questions for everyone:
1) Anyone done this before and have a recommendation?
2) Anyone know exactly what the towing hitch kit consists of?
3) Anyone know what the part numbers might be for everything except for the hitch itself? (a side note here - does anyone know if there is a parts catalog available anywhere for the Cayenne as this would be a huge help).
4) Any idea what Porsche will charge to enable the control unit?

I'm likely to try and go down the option 3 path in any case and will post photos/description of the process to make this easier for others in the future. Thanks.

Andrew