Newbie - Ventilation fans?

Hello, I am a newbie here and I've been looking all around the forum and I do apologize if this has been discussed before... I'll explain. I just bought a 2011 Mercedes 144 wheelbase short roof. I bought the cargo van and put in the Mercedes windows in the front section. I am in the middle of converting it to a touring vehicle for a band. A wall is going up to block off the the back area for equipment. The thing I'm worried about right now is - I didn't get the rear air conditioning unit and the rear windows in the passenger section don't open. I think it may get stale and too hot or cold (also the Sprinter is Black.) I am considering putting in one or two ventilation fans but it seems a little scary to cut the roof. Have any of you had good luck with them? I was thinking solar...

This is the fan I am considering...
http://store.sundancesolar.com/ststsove.html
What I'm looking for is something to cool down the Sprinter when I'm not in it and help with ventilation. I've been looking at ventilation fans and it seems most are for RVs. I'm hoping I could close this off and not have any wind noise while driving.

Here's one that others on this forum have used. It' moves a lot of air, well made. I'm ordering one for my cargo area this week and will install another in the passenger area when I get to that part.
Little pricey but you get what you pay for.
Your AC and heat will keep up if you have it partitioned off and insulated though. I'm putting this in to move air when I'm camped or parked.
http://www.maxxair.com/

Almost all the DIY'rs put in a Fantastic Fan or the Maxxair.

The Fantastic Fan folks have legendary support for their product.

You can also replace any of the fixed glass with T-slider windows. Works well in combo with a roof fan since it gives you screening if you need it.

go to cyclevan.com they have mini side vents for sprinter vans