Dirty MAF will cause other issues, but probably not what you are experiencing (but yes, definitely clean it every once in a while).
I do agree the symptoms could be the IAC, but it's also likely to be the fuel pump, especially if you've never changed it before. I'd certainly start with a fuel pressure check (by putting a gauge on the fuel rail... your year doesn't have a pressure sender) before throwing any parts at it. Or start with a fresh fuel filter if it's been more than 30k since it was changed last.
The IAC is located behind the throttle body, on top of the intake. You'll want to access it from inside the van.
2000 E450 dually V10 wagon