The problem is mentioned in your first sentence; Circuit City. Your car was most likely built before the "tech" was born. If it's not a cookie cutter Scion, Honda or whatever is trendy among the teenage crowd, they won't have a clue.

I've seen several so called professional installs by the chain stores ( and a few by fly-by-night independent shops) and all were hack jobs at best.

Get whatever refund you can. If you don't want to tackle yourself go to a reputable shop thats been around for a while. Chances are they will still have the info you need, either in a manual or filed away in someones head! Go during a slow time and just pick their brain. Might even get some tips to do it yourself. Buy some wire, crimps and connectors from them while your at it.

Some one here might just have that tidbit too.

Good luck man!