Welcome to the Forum.
To answer your question, there are many shops that do top notch bluing. For one, it could go to S&W. There is Ford's who is outstanding and Doug Turbull is another guru.
That said, there are probably 6-12 refinishers in your own state that would do a more than satisfactory job for a reasonable price. Not sure if your in the Big City or the burbs but check the yellow pages. The shop will have examples for you to look at if you are close enough to personally visit.
As to the firearm's value, yes it will be worth less to a dedicated collector when you go to sell it. But I will bet that for every collector that would prefer it left in original condition there are a hundred shooters that would prefer to own a pretty model 27.
I never worry about how much money I am going to make on a firearm if I decide to sell it. As long as I get enjoyment out of it while I own it the rest does not matter. BTW, I have had a model 27 refinished by the factory. After 34 years I still have not decided to sell it. I bet I can sell it for more than I paid for it.
When it comes to refinishing, do not make your decision to please me or another collector. Make your decision to please yourself.