Removing crappy 'overlay' OS from Note 2?

Recently had my S5 nicked and bought a Note 2 (32G).

Nice enough phone/phablet, except that it came with laden with this crappy ‘overlay’ OS by the name of ‘Olleh’ - some nonsense from Korea. Much like Samsung it’s got loads of crappy apps (thankfully no Samsung crapness).

However I want to wipe it and put on a fresh OS, without all the crap. Start afresh, and load up the apps I need with Google Playstore.

Currently running Jelly Bean, phone wants to upgrade, but the guy at the store said avoid if possible (not sure why). I want to upgrade to Kitkat.

Suggestions, ideas and feedback appreciated.