Hi Isabel,
I don't know if the windows will be a problem on your van but the awning is about 11 feet long, we are lucky with ours as we can have it either right at the front or between the first front side window and the door which makes the van lighter inside. The Magnum only needs a vertical strip around 6 to 8 inches wide of caravan wall at each end of the awning for the poles and pads to sit against. Only 1 strip is needed if you use the awning rail on the other end.
If you measure your van from the front awning rail at about waist height backwards, the other end of the awning will be about 11 feet away, if you have no windows within a couple of feet of this it will be fine.
Alternatively measure 11 feet from one side of the door along the van but do allow for the door to open flat against the caravan.
The all in one awnings from Isabella are also worth a look, it depends how much room you need and going from other comments previously made on this forum the repair service offered by Isabella (I have never needed it) is second to none.
spj.