It's extremely difficult, if not impossible, to change the oil pan on a Ford E150 van without removing the engine or at least significantly lowering it. The oil pan is located low on the engine, and access is severely restricted by the frame, suspension components, and other parts underneath. While some vehicles might allow for *some* work without engine removal, the E150's design makes this highly impractical. You'd likely spend far more time wrestling with limited access than you would simply supporting the engine and removing it (or lowering it substantially).
Therefore, the answer is no, realistically you should not attempt this. It's much more efficient and less likely to cause damage to properly remove or significantly lower the engine.
