OK. Thanks guys.
I tend to agree and have come to the conclusion that it would be a bad idea to get that one off ebay if for no other reason than the install headache. I'm not a technician, nor electrician, therefore the plug and play model would adapt much nicer to my lack of experience in installing these things.
I'm looking at the BMWSTX model off bavauto.com It looks good.
Question: Can I assume that my '97 328i is "prewired" for this? How can I confirm? I assume that the connectors would likely be under the dash; but how to confirm they will be the correct ones, assuming I find an open connector... i.e. specific number of wires, etc?
I'd like to think there's a 95% probability that everything would work as described. I'd just like to get that last 5% by confirming the existance of the prewired harness for it...