Thanks Harley Guy! I just read about your aftermarket sensors and may be making that switch soon. I just bought my '07 Expy about a week or 2 ago.
Completely stock with the 20" chrome clad wheels. The Expy has been having the same tire pressure sensor fault warning since day one. The dealership I bought it from is taking it to a ford dealership to fix but after reading the one thread I'm not too hopeful. I may get them to replace the stock sensors with the after market ones you listed.

Just so I understand your answer to my original question. If I get a second set of wheels (which will probably be a set like the ones I have now), when I put them on I'll have to reprogram the computer in the Expy correct? The process looks a little complicated. Did you have to train the system for tire rotation as well?

Edit: I'm pretty sure the wheels are the stock ones. I'm not able to tell since I'm not the original owner.