Have a go at using Samsung Kies to restore the OS. It's pretty straightforward but you do need the serial no. which should hopefully still be on a sticker on the back.
I've used this and Smart Switch to reinstall the OS on a few Samsung phones and a couple of Tablets. Put you exact model number into google to find which version of Kies you need to use although you may be lucky and find that Smart Switch is available for your particular Tablet.
Also, if the Tablet is still under 2 years old you may be able to get it fixed under warranty although after experiencing the monkeys that Samsung contract out the job to you'd be far better doing it yourself.