To change module name:

1- Go to System admin page
2- Hover over system admin and select modules.
3- Find the module you want to rename.
4- In the small form filed in the first column, delete old name and re-enter a new name
5- Click GO at page bottom.
6- Confirmation page will appear.
7- Check the new red entreies and if correct, click go again at bottom.

To change a block name

1- Go to System admin page.
2- hover over system admin and select blocks
3- select the page holding the block you want to change.
4- Find the block and click the 'edit' link in last column.
6- The edit block page has a form field containing the original name.
7- Select and delete the old name and enter the new name.
8- Make any other edit changes to block and save page.