Should I delete and reinstall?

So I am having some major issues with my blog right now. It started when I went to take out the bullets in the Log In/Register meta. I went into General-Template.php and changes the following function wp_register( $before = '<li>', $after = '</li>', $echo = true ) to wp_register('','',true) after I read the Codex.

Apparently I misunderstood what I was supposed to do because I went to load my home page and got a fatal error similar to:

Fatal error: Cannot redeclare tinymce_include() (previously declared in /home/content/j/x/i/jxile/html/wp-includes/deprecated.php:755) in /home/content/j/x/i/jxile/html/wp-admin/includes/deprecated.php on line 25

This wasn’t the exaact error I got, it was relating to the general-template and deprecated.php, I didn’t get a chance to copy the exact error. I tried reverting to the old code and still go the same error.

I then re-upped an old general-template.php and deprecated.php I had from a backup, and instead I got the error above.

I re-downloaded the default installation of WordPress, re-upped it hoping it would fix my issue, and it did get rid of the re-decalre errors, but now when I go to log in I get:

Warning: Cannot modify header information – headers already sent by (output started at /home/content/j/x/i/jxile/html/wp-content/plugins/seo-slugs/seo-slugs.php:87) in /home/content/j/x/i/jxile/html/wp-login.php on line 337

Warning: Cannot modify header information – headers already sent by (output started at /home/content/j/x/i/jxile/html/wp-content/plugins/seo-slugs/seo-slugs.php:87) in /home/content/j/x/i/jxile/html/wp-login.php on line 349

Warning: Cannot modify header information – headers already sent by (output started at /home/content/j/x/i/jxile/html/wp-content/plugins/seo-slugs/seo-slugs.php:87) in /home/content/j/x/i/jxile/html/wp-includes/pluggable.php on line 690

Warning: Cannot modify header information – headers already sent by (output started at /home/content/j/x/i/jxile/html/wp-content/plugins/seo-slugs/seo-slugs.php:87) in /home/content/j/x/i/jxile/html/wp-includes/pluggable.php on line 691

Warning: Cannot modify header information – headers already sent by (output started at /home/content/j/x/i/jxile/html/wp-content/plugins/seo-slugs/seo-slugs.php:87) in /home/content/j/x/i/jxile/html/wp-includes/pluggable.php on line 692

Warning: Cannot modify header information – headers already sent by (output started at /home/content/j/x/i/jxile/html/wp-content/plugins/seo-slugs/seo-slugs.php:87) in /home/content/j/x/i/jxile/html/wp-includes/pluggable.php on line 890

Before it was a different plugin (SEO Webmaster Tools), and I thought I would just need to reinstall it as well it so I deleted it from my host, and now got the error on the above plugin.

Should I just delete all of my plugins and reinstall them, or is there a way to delete my installation of Worpress from my host, and reinstall with my previous posts and content in tact? Any help would me much appreciated, and I don’t want to do anything else to mess it up.