I'm sure others will speak up and agree or disagree with me but you can blow out all the lines and rebuild all the components. I don't see the need to replace the whole system. I am sure the shop you took it to is hoping you believe that you do need to do it and you give them the job. This does give you a good opportunity to learn all about brake systems, DIY.

1953 Chevrolet 3600
Fried Green T'mater (Vern)
In the Stovebolt Gallery
Caution: Political Statement
Man who runs in front of car gets tired, man who runs behind car gets exhausted.