Need some advice on an upcoming head replacement 3rzfe

Hey guys, normally don't post but could use some advice. After researching and testing I have found that I have some burnt valves. I was orinally gonna buy the valves and do it myself with he help of a machine shop but I have decided to just buy a complete head ready to go. I have bought a Haynes manual and been studying up. My question is about the timing chain. It sounds good but i am wondering since i will have the head off if it a good idea to do it. Sounds like some people never change them out but who knows. Any other input you might have about the head replacement would be helpful as well. Thanks