e550SF

I just brought my E550 to the dealer today.

They advised me for a transmission service, brake flush, and power steering flush.

I am planning to buy the fluid online and bring it to my local shop since mercedes wants $500 for the automatic transmission fluid change. How many liters would I need?

Also, is power steering flush necessary? It is not stated in the maintenance manual. My car has 39k miles. If it is, how many liter or quart am I required to purchase?

Finally how many liter is required to complete flush out the brake system and then top it off?

Is Balo the OEM stock rotors? Where is the best place to purchase OEm rotors/pads.

Thank you.