Sewing corner/sourcing clothes

mmm. so, i just found this absolutely HOT dress in an op-shop. think 1950s diner uniform. not one of those ugly white nurses dresses alternakiddies run round in, but a bright blue, giant-collared, flared-skirted diner dress with a logo saying 'Moore' (my mum swears there used to be a chain store in my city called Moores in the 1970s...?)
anyway, the dress is tight, and cinches me into an hourglass, but i need to let it out a little, which is cool, coz i checked and whoever used to own it had it taken in, so i just have to unpick their stitching. but ive just discovered that theyve also taken the hem up, so to unpick all their sewing i have to unpick the hem too, i think, and im a little confused... can i STOP unpicking? maybe ill just stop when i reach the hemline... will that work?

more importantly, does anyone know where i can buy one of those little frills waitresses/nurses (i dont really know which) used to wear in i dont know what era, like a headband or little hat?

im thinking of getting my hair cut into a little curled-out bob too, to match. i really love this dress....

Umm me mum would know should I asker her?

Actually a normal hem is folded not cut, unpick the stitcing around the hem and unfold to desired length, with the letting out bit, just do what you said though be sure to let out the same amount of material on both sides. Dun want a lopsided dress now would you? I meant front and back and left and right, unless it is down the back then you dont have anything to worry about.

i couldnt be bothered to unpick the hem, so i just stopped before the hem. i think the horizontal stitching on the hem will stop the vertical seam unraveling any further...
hope thatll work

I am not a semstress so dun ask me I just knew a thing or two from me mum.