The Sound 5 is the basic radio that comes with the Sprinter. It is make by Becker and includes a disk player but no readily available MP3 player and no Bluetooth.
I decided to replace it with a Sony MEX2500 that I had used before. The Sony has Bluetooth for handsfree phone and Bluetooth for audio.
The first thing is to pull the old radio. That is pretty easy. The size of the Sprinter means you can do the entire operation from the passenger’s seat. No crawling under the dash or trying to reach something just beyond your fingers.
You need a few things before you start. A Metra 99-6512 dash kit (the Becker, although DIN size has an enormous face plate and with this kit you can fill the gap). A antenna cable 
adaptor for use with an amplified antenna. I used an Metra AntennaWorks 40-VW53. It is also nice to have a tool to make removing the trim around the heater controls and radio easier although you could use a putty knife just as well.
This is the nice tool. A assortment of these are available at Harbor Freight that will also give you tools for pulling door panels, headliners, etc.
(Click on the pictures for a larger image)
After pulling the trim you can just let it hang by the wires. You will see the Sound 5 and the plastic pocket below. You can pull the pocket from each side straight out 
- just keep slowly applying more pressure and it will pop out. It is held by a plastic clip on each side.
Now you can get to the 4 T-20 Torx screws that secure the radio. The radio will slip right out. Disconnect the harness connection and the antenna from the back and set 
the radio aside.
You’ll notice that going into the Becker were only 9 wires yet you have 5 speakers so you should have 10 wires just for speakers - well, for some reason unknown the speakers are all routed to just 2 wires. Don’t expect much separation of sound with this set-up.
So now you can cut the plug away from the wires. The antenna connection may look strange (shown to the left) - whatever you do don’t cut the connection off! If you
do, you will have extra work and will have to buy Metra AntennaWorks 40-VW20. And that’s enough said about that!
Now you fit the radio into the new dash kit following instructions that come with the kit. Next you cut away the harness plug and it is just a matter of 
splicing the wires from the radio to the wires in the dash. From the radio the (normally) 8 speaker wires go 2 each to the the the brown/violet (+) and brown/dark green (-); brown/orange (+) and the brown/dark blue (-).
The red/black (upper right) is to the battery. The brown (upper left) is the ground. The brown (upper center) and the brown/red (below the ground) go to the accessory switch. This means the radio will turn off when you turn the key off. If you want this you will have to run a wire from a switched connection on the fuse block. If you want the radio to stay on and only go off when you press the radio’s off button then wire the red/brown to battery wire.
The last wire, the yellow black will have 2 connections. The first to the power antenna wire on the radio and the second to the power antenna wire coming from Metra AntennaWorks 40-VW53. These wires are usually 
blue. Since the Sprinter antenna is electronically amplified you need to do this.
Mount the dash kit and close up the trim. You are done.
The cabinets on the left are over the marine toilet and will have doors. On the right will just be an open shelf with a bar below to hang jackets, etc.
