Make sure your spark plugs are tightened sufficiently. I do not know if the 2002 engine has the 5 thread or 9 thread holes but the Mfr. (Ford) torque rating of (I think) 17 Ft/# is insufficient to keep the plugs in.
When they go, they take the coils and possibly cyl. head with them. Take them out, clean/inspect and/or replace if necessary but tighten them properly.
Here is a link to a site that is run by a guy who makes his living (or at least part of it) repairing these engines if they have had this problem. His recommendations re: the preventative maintenance seem solid.
http://www.blownoutsparkplug.com/index.htm
And another which "suggests" that Ford has authorized them for these types of repairs.
http://www.fulltorque.com/sparkpluginserts.htm
They are also known for having some issues with plug wires but I suspect that the later models had the coils connect directly to the plugs without the wires but JIC...
http://www.magnecor.com/magnecor1/cop/f ... 0.htm#pic1
As always, YMMV...but an ounce of prevention...as I tend to be proactive rather than listen to those who "have never had a problem so why mess with it" types. If it wasn't an issue, why is there a HUGE class action lawsuit out there re: this/these problems. If it were me, I would check it and fix it if necessary...and then enjoy the coach!
Good luck.