Kindle Fire Freezes, Overheats, Browser Constantly Crashes

Hello Guys: I've had this Kindle Fire HD for nearly three years now and for the past few months it has gotten worse and worse. Basically, as I mention in the title, the unit constantly freezes, the browser crashes over and over, and the rear left of the Kindle (around the middle) gets pretty hot. My question is: What internal part can I replace to hopefully fix this issue before this tablet burns up altogether? If anyone has run into this issue and managed to fix it, I would very much appreciate the guidance. Right now I just have no clue which part, if any, could be defective and in need of replacement. Or maybe more than one part is faulty. Please help. Thank you kindly for your time and I hope you have a wonderful day. :-)

Cordially,

Robert D. Johnston