Yep, install done myself, easier than you might think...
And your right, there is a clear spot marked on the inside, from the factory. It's not cut, it's just marked..
I just used a hole saw attachment on the drill to go though the plastic from the back, then stopped when I got to the trim, and used a stanley knife to do the rest.. worked out really well..
I was so paranoid I was going to bugger it up, as you probably are...

The below site helped me ALLOT when I did my install. Probably been linked to a million times on here but I'm new

http://www.integracaraudio.com/caraudio/diagrams/