Insulate Box?

it is always in my opinion a good idea to insulate your box ,this helps with the boominess(standing waves)a generally raises the Q slightly helping to tighten up the bass. you can port almost any box given the right parameters and speakers but it is more to it than just cutting a hole in it.if tuned incorrectly it can lead to weak bass or increase boominess,personally i prefer a closed box myself. 

do I just stuff the box or line the inside if so what should I use......

Does the manufacturer recommend a ported enclosure for this sub?  Do you have a manual with it?

As for acoustical stuffing, it works well in a sealed enclosure to deepen the bass, loosely filled.  No more than 1/2 lb per cu ft.   But a ported enclosure is (usually) a larger box than a sealed, and doesn't benefit by using it.

Find all the info you can on the woofer.  if you want to find a good calculator to help you build a new box, we can help with that.