Greetings Sir or Madam and welcome to JA! I will do my very best to assist you with your problem.
Are they replacing the tensioners as well?
Ok, as a general rule, if you have noise at startup then they should also be replaced. I would of course have this diagnosed prior to just doing it. The whining isn't really that common for the chain, but the rattle sure is.
As for the quote, it is within reason. I am showing 8.5 hours labor for the chain, then with the extras, tensioners, oil change and coolant I think it is an ok price. Especially at the dealership.
Hope this helps! Please reply if you have more questions!