you can absolutely do it yourself. be prepared and get the right tools, look up many many guides and videos before you start, but I honestly think it’s doable for someone whose never opened a phone. those batteries are an absolute pain in the ass to remove, but as long as it’s discharged below 20% you really don’t have to worry about it it catching fire or anything catastrophic like you’re lead to believe (just be careful ofc and wear PPE)