Yes, yellow is your constant power and red would be the memory. Black is always ground. What brand deck is this? It's my experience with JVC's that they have things like this happen often. Also, where did you buy the deck?
That's a hefty load on any car. First off, you'll need to have atleast 2g wires for everything. Make sure your alternator is directly connected to your + battery terminal with the 2g wire and reground the alternator with the same wire. I would definatly suggest running a second battery in the...
The most "out of the way" place for an amp is on the underside of the rear deck between the rear speakers.
As for ported or sealed on the L7...I definatly suggest ported. I'm an installer at Circuit City and we won't install L7's in sealed boxes. They have a good tendency to blow in sealed...