I've been looking it up myself, and people say to turn them inside out, but Idk about the inner lining. I was originally just thinking about cutting it right on the outer seam and folding one side over the next until it gets to the right tightness then sticking it with a sewing machine.
I'd suggest a tailor, unless you know someone that has an alright understanding of sewing and has a sewing machine. Essentially what you would do if you do it yourself is cut off the seam, then sew it up. Sounds easy, if its your first time sewing. Trust me its gonna take a long time