PageOfPosts.php template

I’m trying add a pageOfPosts.php template to the twenty ten theme which the non-profit I’m volunteering for is using.

The php code for pageOfPosts.php is found here:
http://codex.wordpress.org/Pages#Creating_Your_Own_Page_Templates

This code uses a function
twentyeleven_content_nav
which is not available on the twenty ten theme, so the change doesn’t work.

I’m not a php coder but I am a software engineer so a few tips and I’ll figure this out.

Can I just add this function to the functions for the twenty ten theme?

Is my best bet to update to the twenty eleven theme? (Your experience with this update especially appreciated.)
thanks!