Those things they want to replace, very well could be bad. BUT their excuse is one of the largest piles of horse shit I've heard. Ask them this "When winter roles around and my bike is sitting for close to 5 months, will I have to replace all these things again?"
Your bike is 10 years old, all the things they listed are things that seem somewhat understandable for a bike that old. However, the tank flush and the new brake sound odd to me. You should be able to look inside you tank to see what kind varnish or rust is in it. I'm not too sure about the brake, do they want to replace the whole thing, rebuild it or what exactly do they want to do? If they are only going to rebuild the brake, I don't see that as a bad thing.
If you don't feel like you're getting a good deal take your bike to another mechanic.
there's hope in the words and emotion in the eyes
it's so easy to be misled by the savvy gentle guise
and like fools we trust the delivery
but it's all just drunk sincerity