I'm gonna get smash on the Wii U hopefully in a few weeks. I enjoyed it on 2DS when I had it. I sold it thou since the Wii U version is almost out. Some people mentioned similar issues with the circle pad. A lot of them said they bought the parts and installed it themselves. Where they bought the parts idk but I figure ebay or even amazon . Battery wise I'd check amazon if your fine with buying from them. They normally have stuff like that. Hope u can get it fixed or replaced soon.
Congrats on your achievement!!!