Plug-in crash causes admin trouble

Hi!
I added “head and footer” plugin. Pasted my google-analytics tracking code in the “head” and than I lost access to my admin-login page. The problem is caused because I had already installed the Duracell google tag manager plug-in. Seems to me they crash against eachother. And I should have been smart enough not to install both. But unfortunately I was not – and now my adminpage is kind of lost/and I cannot log in to i anylonger.

Is there a way to remove the “head and footer” plugin – or disable it. I have searched the forum for help – but it seems difficult when I cannot anylonger login to my blog.
This is the message I get when I try to login:
Warning: Cannot modify header information – headers already sent by (output started at /home/content/p3pnexwpnas09_data01/12/2755712/html/wp-content/plugins/duracelltomi-google-tag-manager/public/frontend.php:410) in /home/content/p3pnexwpnas09_data01/12/2755712/html/wp-login.php on line 42

My site is: tennishjarte.com