Going to do an os upgrade to 7. Is this dlc a new standalone game or do I need to save my old files. I was going to just do a fresh install of everything. Seems like the best idea.
It has the same concept as Dawnguard:
It is not standalone.
You may have to be a certain level to "officially" start it.
Works with new and old saved games. I also haven't had any problems with the mods I'm using (around 90 esp/esm mods and many retextures/remeshes).