Sounds to me like you will need either a new cord or a new battery. Try using a cord from a different device (as long as it works for it) to see if it will charge then. If it will, you are good. If not, then you may need to replace the battery
And contrary to what they say, you can replace a battery in a tablet.
It just isn't so easy or simple in some of them.
If the device is still under warranty, I would contact the manufacturer before doing anything and voiding that warranty.
If it is no longer under warranty, then you are free to do the work yourself (if you feel comfortable doing it) or take it to a local tech/repair shop.