Please, find attached a simple application that demonstrates how to handle the GridViewCell.EditEnded event. It also shows how to hide a grid column runtime. Please, let me know if the code works for you.
Regarding the setting the header text of grid columns: the currently available version of RadGridView has a bug which prevents the headers from properly updating their UI when the developer changes the HeaderText property of a column. We have this problem logged for fixing, we will try to include a fix in the upcoming major release Q1 2009 in a couple of weeks.
All the best,
the Telerik team