I used to feel this way too when I began buying luxury ~7 years ago so I totally understand. I’m sorry you have a hard time with anxiety, thank you for sharing with us. I have never been to any shops in the region but I do have a nice (though gruff but very helpful lol) SA I can pm you at bloomies. I’ve always heard good things about 57th and if nothing else, there is likely more selection so I agree with others recommending that store. I would also check out the SA recommendation thread as many great SAs have been shared there and you can likely make an appointment in advance. You can go in with a trusted entity that is known for being helpful. That for me would set my mind at ease - going in kinda ready to go and without ambiguity of what they are like and when I’ll actually get in (due to possible lines or pandemic entrance limitations) would be good because you can know you won’t be hungry, have your hair tidied up in advance, etc.
Personally, I really love to dress fashionably or dress up (I live in sf so... honestly standards here are so low for fashion lol! Patagonia tech bros galore) and that has always given me not only a creative outlet but helps me feel secure for what the day may hold. Perhaps you can pick out an outfit in advance and just know you feel comfortable and confident. That way you can make sure you don’t have wrinkles or it doesn’t fit right, so less things to stress about! Also comfy shoes are a must.
If you are considering another smaller purchase to build history, I’d take a look at their beauty section because they have a virtual try on online. You can test out which lipsticks look good on you, or research a perfume or face cream you may like. I personally love Les beiges lip balms (any shade) and they’ve saved my lips this winter. Yes they are pricey but if you have the extra money for it, it can be practical and help you have a history in store.
I wish you the best of luck and hope you get the dream bag you desire!!! I think everyone else’s tips here are great and you got this. Congratulations on enjoying this wonder for yourself, these items are pricey but absolutely should last a lifetime, and I hope that when you gaze upon it, it reminds you of a memorable trip and a proud accomplishment to be able to get it.