You can animate text to do just about anything using Text Animators, but yes, it's usually a good idea to create the elements that comprise the scenes in your animations as separate layers.
You cannot import 3D text layers into AE anymore as 3D layers. You have to rasterize them. If you really need 3D text in your design then there are many other options for doing so in AE.
Here's the deal though, creating a successful animation is a lot more complicated and requires a lot more time that you seem to be expecting. Just getting the timing right takes some folks months or even years to learn. Sure, you can buy a template that has lots of cool moves and drop in your own graphics and produce something that may look pretty professional in just a few hours but effectively telling a story is a lot more complicated than just making text fly around the screen to the beat of some music. You have to understand how the eye and the brain interpret movement, contrast, scale, color and how those elements of your design work with sound. If you have a really good understanding of those principals then mastering the tools in AE so that you get what you expect is going to take about 10 times as long as you expect it to. Polishing those skills so that you don't need to do a full screen ram preview or render your project to see if it's going to work can take years.
