Well, Larisa, rather than contributing another personal story I'll simply give you advice for you situation based upon decades of wearing long hair. You are at a life crossroads at which you are trying to be two different things at once. This is just the beginning of the difficulties you'll experience. Sooner or later everyone you work with is going to know you are transgender. I'm not sure there's any advantage to waiting until later. Think about that.
As for long hair acceptance, people always react (often negatively) when someone makes a major hairstyle change, but they usually accept it after a time. The very best way to hasten acceptance is to do everything you can to make your hair look as good as possible, whether long or short or masculine or feminine. I've always tried to wear my long hair in well-trimmed, well-styled ways, even if the styling is decidedly feminine. Surprisingly, people tend to be more accepting of this even if you present as male. Go the extra mile and avoid the bad hair days.