There is the E-Series owner's manual included in the paper work. That has a maintenance schedule for the engine.
The Cummins guys gave me a schedule for changing the genny oil (something like 50 hours, 100 hours, 150 hours, then at each 100 hours after that).
Given our usage pattern I'm planning on just having both (engine & genny) changed at the end of the season each year (we'll be putting around 5000 miles a year on the unit max).
Thanks Jamie, I found the section that says "7,500 miles or 6 months, whichever occurs first" in the Ford book. The dealer loaded me up with all kinds of material and it took about 2 hours today to go thru it all. happy new year!