Anyone else have experience with Priuskings?

I just bought a 2009 Prius that has 143k miles and was apparently sitting around for a few years on a farm, yeah its one of those smelly Prius's. I am aware of the battery malfunction in this car and when I drive it the charge barley lasts 15 seconds before going into the purple bar. Anyway I have a local mechanic who is willing to do the switch for me free as long as I have the new battery. I am confident I want to buy a battery, but I was checking in to see if the community here has had any experience with these guys?

Thanks