I figured I may as well post my crappy cellphone pictures, even though the rest of the information in the thread is more informative. I overexposed the pictures as much as I could so something would be visible...
Here's the generator as seen from behind the van through the space between the hitch and the bumper:
This one is from the rear looking up and you can (almost) make out where the exhaust pipe leaves the right side of the generator on it's way to the left side of the van. The little flat spot diagonal to the front is where you gain access to change the spark plug and if you look really, really carefully you can almost see where the green begins, a black cover which you would open to check the oil and change the air and fuel filters. If you can't see it, you can take my word for it, it's there.
This is a view from the left side, and you can see the oil drain plug, the exhaust on the left side of the generator "box" and more or less where it is located in relation to the van's exhaust.