Personally I would not try to replace the battery, that thing is really old and its Android version obsolete.
Also, it being a tablet could mean the battery is glued into place which makes replacing the damn thing complicated and expensive.
Indeed. It might damage it even further. I used to have a 7 inch Samsung Galaxy Tab 3 which doubled as a phone but that thing was neat to open and the battery was actually replaceable despite the warning not to do that in the manual, but a decent replacement cost about half the price I payed for the tablet / phone. It also stopped being a phone when I damaged the sim socket by accident