Issues using "Global Product Categories Solved! A tutorial"

After following the tutorial for how to create global product categories for my marketplace, I found that the plugins created a lot of dead links for my site.

After creating the mu-plugins style-wp-admin.php and wp-admin.css, I was able to get rid of the "Add New Category Link", but then I would get blank pages after trying to perform any other command on my site (Ex. Save Changes, Log Out, etc.). Also the Network Terminator Plugin wouldn't display anything after I network activated it.

Are these issues occurring because marketpress & wordpress have updated since this tutorial was created? All help would be appreciated!