I think it would be great to be able to solve more kinds of PDEs. It
would have helped when I took similar courses in college.
If you feel comfortable jumping right in then jump right in. If you
are unsure, you can start with an easier issue. There are no
requirements that you do one thing before you do another thing with
respect to contributing. There are generic guidelines for
contributing (see
https://github.com/sympy/sympy/wiki/Introduction-to-contributing and
https://github.com/sympy/sympy/wiki/Development-workflow), for
example, all new code needs to have tests. But if you miss anything
we'll let you know when you submit a pull request.
Aaron Meurer