Melanoma Type 1

Hi,
I have been diagnosed with a type 1 melanoma on my left leg (a new mole…)
I will undergo chirurgical operation to remove it in two days.
My doctor ensure me there will not be anything left, and not any problem at all, but I am so scared it could already have spreaded somewhere else in my body.
What should I do?
More analyses (which ?), diet, supplements ??
Please help, thanks a lot

Lolla