I would like to help you in this project. I'm new to this platform, and I'm looking to win some positive reviews, so I would participate in this project for a really low price. You can see here an example of an animation made by me, using After Effects, so you know the kind of quality you can expect if you decide to hire me: [login to view URL]
There are different techniques to get the animation of the mouth, and depend a bit on the type of result you seek to achieve. The two most basic are those that use several different mouth models in different layers, and the one that uses vectorized curves to directly deform the shape of the mouth. I would need to have the file of the character you have created, to tell you which technique is most appropriate.
I hope you are interested in my offer. I promise to have a great communication with you, and to give you a result that really pleases you.
Greetings.