Big daddy, the chassis battery disconnect is right above the accelerator pedal. Push down on the red button, then pull straight out. You'll see the deal. Always wait at least 20 mins. after turning engine off to do this disconnect. It allows the computer system to go through all it's shutdown steps.
The usual term for the "shore" battery is house or coach.
You have a lot to learn about Sprinters. They are not the simplest vehicle to keep up correctly. Your 2008 takes special oil too, assuming it's a diesel. Not an off the shelf product. Read your Sprinter manual cover to cover.....