Been a while since Ive played, I was wondering is it necessary to merge leveled lists when running a number of mods, and how would one go about doing that.

You basically need Wrye Bash to do that. Whether or not merging is necessary depends on what combination of mods you are using, however.

Wrye Bash -http://sites.google.com/site/oblivionpoinfo/prep/wrye-bash <-- Please let me know if any of the instructions are confusing. There is a link to the site's thread in my sig. Please, post questions and feedback about the site there.