Think of it like this. If you rebuild an engine, and it shits itself, its costly, embarrasing and generally its an inconvinience to your every day life. Who's fault was it? Yours, you built it right?
Now, You have this fancy, sought after car that is a common target for car thieves, EVERYWHERE. You install an alarm, it all seems good and well, and you may even have followed the directions like a pro. Now, some car thief comes along, who is 99% of the time clued up on most car security systems, can see that its a basic install and easily bypasses it and takes your pride and joy. Now, who's fault is it? Yours right? you installed it. AND THEN.....
The insurance company comes along, asks the general questions, and asks who installed the security system.......see where this is going?
IMHO, take it to a professional, not just any, but a PROVEN AND REPUTABLE professional, get the job done A1 and hide the bastard well. Its peace of mind mate!