I purchased my alarm through Rob_. Although he isn't available anymore, he did leave contact information for someone else to help us out.
http://www.x3world.com/x5-e53-forum/...t-contact.html
He charged me about $190 for the X3 alarm kit, shipped. Based on what the list price is, and dealer labor rates these days, your quote seems about right. But why have a dealer install it when you can do it yourself. Mine came with all instructions and it was not hard at all to do it. Definitely less than an hour, and if I had to do it again, would be less than 30 minutes. If you had/have any install questions, please feel free to ask me.
I say order it from Rob_'s new guy and install it yourself. The only thing you will need to do it take it to the dealer for coding. It takes no more than 10 minutes to do that. This method will save you a few hundred dollars.
Either way you go, good luck
