Hey there! I too spent so much time on a skin I was working on, and when I uploaded it it was backwards I can't necessarily fix it for you, since I see a lot of time has passed since then, BUT I will tell you there is a website that reverses the skin (NOT INCLUDING THE HAT EXTENSION) for you! I was so relieved to see it worked. Alls you have to do is redo the hat portion. I hope it works!
I'm reading that a lot of people are needing help.... and I kinda feel bad for asking for help too... But I just tested my skin I made and realized it was backward. I realised that I edited my skin using the back as the front, so if there is anything anyone can do to help that'd be great!