Section wizard removes changes made to code

Hello,

I am trying to add an image field to a fully user generated section in my custom package. I have it working, but when I make a change to the page using the section wizard, it deletes my edits to the diff and methods areas which added in the functionality for the image. How do I add the image method and diff to the page and keep it while making other edits? I tried to do a replacing page but it says I can't make a replacing page in the same package. Then I tried making another page that doesn't replace the parent and it didn't work. Thank you.