I think you should start by choosing which software you will want to use. There are various options. Adobe Fuse and Blender are very popular in the industry. Then once you do, try to look for an affordable course to learn it. I haven't done 3D animation, but I know it's a pretty popular and in demand skill.
Wow! 3D animation sounds really cool! It looks difficult and complicated. I'm not trying to discourage you though. I think 6 months would be enough to learn to use new software, but it depends on how much time you spend on it.
I am a big fan of Adobe, but their software tend to always have a steep learning curve. At least, this is what I have experienced (especially with Illustrator and Premier Pro). I am not saying it's not worth it, not at all. I am just saying that you should prepare yourself to spend a lot of time learning. Good luck