The flush at 30,000 is a good idea....I don't know why Ford waits until 45,000 miles for the first flush, then after than, every 30,000 miles. I wouldn't change the thermostat until it gave you trouble. Too much potential for leaks if its changed for no reason.

-Mark- '99 Mystique LS, totally original (including the original water pump and the premium stereo)! Bought new in December 1998 for $21,000. 208,000 miles