New member needs advice

Hello all, I am new to firestick, so I hope I am posting this in the correct forum. My first question is that I have a firestick with V15. and it also has Kodi. Is it easy to upgrade it to V17?
Question 2, is that I want to purchase another new stick on eBay. What advice would you have for me to purchase?
But, the firestick with v15 was giving to my wife a few months ago and it just got a chance to plug it in. We have 2 TVs so I would like two sticks with kodi for each TV

THANKS for your help, steve