First off, Welcome!
Its nice to see there are some females out there that care about their truck. There arn't too many on this forum and the more the merrier
. About your changer idea. You can ALWAYS add a changer. Whether or not its directly intagrated into your stereo is another story. I'll look around on the net, but I'm almost positive you can add one onto your existing system (ie no extra remotes etc.) About the bass. Thats pretty easy too. I would order an infiniti bass link or bazooka tube that has the amplifier built in and can be adjusted to your bass needs/wants. Let me look and see if i can get something on the changer.