Replacing a full car battery, especially one as heavily used as a hybrid battery, is nothing like replacing the battery in your TV remote. It is an extremely delicate, complex process, and, if approached incorrectly, there is a very real risk of electrocution and severe injury. Unless you are an extremely experienced D.I.Y. expert, any money you might save isn’t worth the potential for harm.
Toyota doesn’t offer official documentation for replacing a Prius battery home, likely because they’d rather not be liable for people who try on their own and get injured. As such, if you wanted to do this, you’d need to consult a D.I.Y. manual or video, which may be out of date or just flat-out wrong. Also, in the event something goes wrong with a replacement at a licensed garage, they’ll usually provide compensation and replacements free of charge. If you do it yourself, you’re not getting any do-overs in the event of a hiccup.