If you have the proper tools, you can easily change the serpentine belt yourself. It is not hard at all and definitely cheaper as 200cdn.
I have recently renewed the O-ring in my thermostat housing (it was leaking) and wanted to change the coolant as well, since it has been on the engine all the 370.000km without ever being changed.
When I had the coolant out, it was looking as good (and maybe even better) as new coolant, so I brought it back into the coolant system. MB coolant is great and stays very clear as long as the engine doesn't spill oil in it.
with a minor 600+k