[Rabin Shrestha]

Hi lisa,

If you had made changes directly to the parent theme, yes your changes will be lost when you update the theme. If you are making simple CSS changes you can use custom css box in our theme options panel to paste your css. Also the minimum requirement for a creating child theme is a style.css In the child style.css you can write css that you would like to override of parent.

For changing the php code you have to create the functions.php in your child theme then unhook the particular function of parent theme and hook your function with the changes.

For more detail have a look here http://codex.wordpress.org/Child_Themes

Rabin