Yup, it's both expensive and addictive! But, if you plan well, do your research, and install it right, it's worth all of the money an aggrevation!
You're on the right track so far. Read everything you can here. Find out what others have done. What works, and what doesn't work!
I'd suggest that you:
a) put your general location in your personal information so, if someone's local to you, they'll know it. I know that I've contacted folks when I've seen that they're local to me.
b) along those same lines, check out any local meets. In our area (Washington DC / Maryland / Northern Virginia) there's a meet just about every month. It's great to see how different people have different solutions for similar problems. Even if you don't have a CarPC, you'd be welcome. Personally, I LOVE showing off my hard work!