Amp - Why not use a car amp? Is there some reason you don't want the remote turn on (don't you want the amp to turn off when you turn the car off?)
Power - Use a 7805 regulator IC or similar.
You can get the dock connector plug from mouser - I have the part number somewhere, I'll dig it up for you if you can't find it on the interweb.
I take it when you say the ipod died, it's just the HD and the rest still works?