Update: I got my beige claire bag back after ~ 1 month -- not very happy with the results and I will be bringing it back to Chanel probably since they didn't get the stains out. In my case, it looks like they do just re-dye the bag, as I notice the threads around the parts that they re-dyed are darker than say the interior. So I am not really impressed -- thought they would actually have better attention to detail and care for the price ($285). Also, the hardware came back scratched again.
You should inspect the bag before paying the fee in the boutique. I brought my White jumbo flap for leather refreshment. They came back in a month didn't do a good job, so I told them to re-do the work. They only charge me one time fee. I'm not sure will they charge you again if you bring it back.