Gradually change out fluids as you can... most benefit from age vs. mileage change. Your owners manual will specify fluid changes at age or mileage increments.
I'm working on swapping out my car's fluids over a couple of driving season's hibernation time.
Last winter was brake fluid and trans fluid; this winter is coolant, water pump and low-temp thermostat.
By DIY, of course. These cars are pretty easy to work on with a Bentley manual and this forum to reference.
