Looking to get new battery and new GPU and possibly the best cooling.

So i have an alienware 17 battery is pretty toast so needs to be in adapter permanently or deflates quick off power line. So any way to replace this or get a new one? Also looking to swap out nvidia GPU for a better one if possible and which one would fit it? I changed the hard disk to an SSD already and i have a pretty nice cooling pad l, but wondering if there is a preferred pad to buy for it. Anyways i like it and want to keep it and it performs well already just want to fix it up if i can.

Please help a tech guy out. Let me k ow if more info is needed thanks ahead of time.