Child theme for Wordpress/Woocommerce site

I need someone to create a child theme for my Wordpress site which includes Woocommerce. The problem is that I forgot to create the child theme before I started modifying the files. So I need someone to go back and see what was changed and create a child theme from that. I assume this can be done by comparing with the original unchanged theme files, but don't have much experience with this so need someone who know what to do in this situation. My site also uses Woocommerce and I have made changes to some of the Woocommerce css files, so I need something to be done with them too. Overall, the changes to the files aren't a lot--I just can't remember what was changed. It's very important that my site looks the same way it does now after the child theme is created and that it will be OK for me to update my theme and Woocommerce in the future without losing any of my changes. When you bid please give an outline of what you will do to fix this problem and what information/files you will need from me. Thank you.