72' p30 Stepvan conversion windows question

[Steppie]

I was wondering if anyone has any advice for cutting a window out of a stepvan. I am not sure what size window yet. Will be a sliding window so I can open it. Also, I want to cut a sunroof in it too and round out the squarish wheel wells in the back. What is the best way of going about it and do I need to shore up the window? The panels seem kind of flimsy and I have not done anything like this before. I am thinking an angle grinder will work for cutting.