It is not easy to teach kids in general. It is even harder to teach special needs children!
Working with children that have special needs is very difficult from various points. First, you truly need to have the emotional make up to see and work with children that struggle (on varying degrees) and how they cope with their difficulties. Second, it can be very physically draining depending upon the environment, disabilities of each child along with the interactions that the children have among themselves. Third, the teacher of the class is a make or break point. Some are great, while others are not! The teacher can be a wonderful resource for you as well as a terrific mentor but on the flip side, they can be a horror.
The pay for a teaching assistant is usually on the minimal scale however it does vary and that is something that you would have to research prior to diving into it.
The most helpful suggestion would be to see if you can get an internship where you work within several special needs classrooms over different venues. For instance, in a self contained classroom, a therapeutic school, a regular education school that has special needs kids mainstreamed, etc. If you are unable to secure an internship, inquire as to becoming a volunteer if the hours coincide with your schedule. Explain to administration what your goals and hopes are and ask if they would be willing to help you discern if this is the path that you would like to take.
There are many levels that encompass special needs children along with various and numerous disabilities. Try to secure as much experience as you can before you decide. If the classroom setting turns out not to be what you want, there are many other positions that are available where you can still work with special needs kids and make that incredible difference in their lives.