How much should a software update cost?
 

I have a 2008 Mini Cooper S. Recently, the "Engine Malfunction" light showed up and I had reduced power to my car. I took it in to my local import mechanic to get it diagnosed. He says it needs an oil change (90 dollars for some reason) and an ECU software update. He tells me that the latter will cost me 600 dollars.
I will be contacting other import mechanics tomorrow to ask about the process, but that feels like a ludicrous price for a software update.

I cannot afford this repair, if I decide to only get an oil change, will driving the car without an updated ECU damage the car further?