Connecting my iPod to my Car's 30-pin Dock but Being Able to Control It from Within the iPod?
I don't think that you can override the car's interface when using the 30-pin connector with that iPod.

If you use an aux cable (1/8" male to 1/8" male) to the headphone port you will be able to control the iPod using it's native interface, but you will lose the charging capability. To regain charging you could use a 12-volt power adaptor, but this is two cables instead of the single cable you are currently using.