1. Have you probated her will? You need to consult a lawyer if you haven't already.
2. By all means get an accountant. You need to file a final 1040. Fortunately, Texas deadline is in June this year, but that's not that far away.
3. You are not personally responsible for any of her debts, but as several others have said, her estate is responsible for any and all debts.
4. Depending on the complexity of her estate, this can get pretty complicated. Get help!
5. Estate tax only "kicks in" if the estate is over 6 million, or at least that was the number in 2016.
6. Every year or so, I still have to deal with my parents' estate--my dad died in 2008. Keep that paperwork forever.
7. Someone mentioned a POA--that ended when your mother died, so it doesn't make any difference now.
8. Good luck!