2013 Great West on a 2011 Mercedes Sprinter?
I think it is Mercedes option code SH9 (or SH6 or SH7) you are looking for. I'm not 100% sure. I suggest checking with Mercedes to know for sure.
SH9 - Airbag, Driver/Passenger Window - $720 Front curtain airbag
SH6 Airbag, Driver Thorax - $300 -D side airbag
SH7 Airbag, Driver/Passenger Thorax - $420 -Front side airbag
On my GM van there's a sticker with the list of RPO codes on the passenger door. Those codes are all the options my van came with from GM. I entered them into an online decoder and printed out all of my van's included options. Maybe your Sprinter has a similar sticker.
If there is a Mercedes dealer nearby they should be able to tell you every option that your Mercedes came with. Maybe they'd even give you a print out.