I have 53,000 miles on my 2000 ML-320 and I believe it's time for a coolant change?

Can anyone tell me the proper proceedure for changing the coolant?

Does it have to be flushed or can I just drain it and refill?

It looks prety clear and clean, but it is approaching 5 years.

Also is Zerex G-05 ok to use for the replacement?

Thank you