Actually once a pineapple is picked it never ripens. So when you pick up a whole pineapple in the store just look at the bottom and give it a smell. If it smells nice and sweet and the outside of the pineapple is golden yellow then it's a good one. If it's green then leave it because it will never ripen.

With regards to cutting it up I just cut the top off and then cut all the outside off. I cut up the flesh and put it into a airtight container in the fridge. Fresh pineapple doesn't last long in this house so I couldn't really say how long it will last for.

Enjoy.