Changed mine preemptively last Spring at 100k - still looked fine(FWTW). Should have done the thermostat at the same time - the temp gauge is reading lower than usual now that cold weather is here.

Mine did have the plastic impeller. Replaced it with a "Graf" with metal impeller from Autohausaz.com - 'bout $60.

Prob'ly do the radiator this summer at around 125K.