HI, CHOPIN
It was my experience that the Chanel boutique on Madison Ave. has a much more welcoming atmosphere/staff than either the one on 5th Ave. or in Soho; my SA, Ms. Rowe, is especially lovely.
But if you're still feeling intimidated by the prospect of taking your I'm-not-positive-authentic bag to a Chanel boutique, those of us who live in NYC have so many more options than women in most places. Artbag -- at Madison & 81st St. -- gets rave reviews in NYMagazine, Vogue, etc. And I've also heard some good things about 2 other places, Hallak and Meurice.
Wherever you go, I hope you'll post back to let us know how you make out. Good Luck!