The outer pane should be a standard Dodge Sprinter sliding door fixed pane window which is held in place by the black standard window weatherstripping/mounting. (NEED to double check measurements/dimensions.)
The inner pane is a Westfalia item and looks like it is glued to the outer pane.
The interior gray plastic roll-up screen and surround may need to be removed for easier access.
Before doing anything, check your insurance to see if covered and how much deductible.
2. Outer Pane Replacement
The window size for the sliding door is DIFFERENT than the window size for the non-sliding door size, so need to be careful to identify right part. Replacement originals can be a fixed pane orna half slider.
3. Body Shop/Window Replacement Shop--Same Outer Window Pane
Find a good body shop or replacement windshield/window shop. Ask them re cost of a replacement Dodge (or Mercedes). They can look up or you can ask a Dodge or Mercedes dealer for correct part number.
Have them examine how inner pane is mounted and whether they can remove and reuse.
If you are handy, you might install a replacement pane yourself. There are posts here (search OneManVan and this subforum) on how to install a sliding window on the driver side.
5. Alternative Option--Half Slider Window
If you don't need a double paned window on the sliding door and would prefer a window which can be opened, you could do that.
As bad as it seems, you may indeed be very lucky, as the outer glass is easily obtainable. The inner glass may be unobtanium.
A competent glass shop should be able to fix this. First, if you're at all handy, I'd recommend striping down the door and keeping all the tiny pieces for yourself. You need the attached documents. You may or may not have to buy a new lock knob; contrary to what it says in the manual, ours just unscrewed.
Behind the blinds you will find two angle brackets that attach to the door. Label those right and left, up/down etc. and take them off too.
The glass shop should measure the gap between the two panes (perhaps spacers are required?) and then glue them together with the appropriate adhesive. Replace the gasket while you're at it!