Will I be able to un-install the DLC if I dont want it anymore
Yes. You can deactivate it in the Skyrim launcher, and you can also completely delete it through Steam.

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Tough it is outdated now. 7 is good and with Microsoft's tradition 8 will svck, so 7 will be the most used one for many years to come 
Next question is, will the new DLC automatically overwrite the Skyrim HD textures? I installed it as a mod with NMM I don't know if that means they are 'loose' textures and I don't know what a bsa file is so the explanation above doesn't tell me anything.