It might seem overwhelming at first, but remember you are not alone. There are lots of people, like your parents and/or guardians, friends, counselor, college advisor, and teachers, that want to help you succeed.
The College Board has put together some very useful advice for undocumented students in a short report called Advising Undocumented Students 2010.
The George Washington University HEATH Resource Center at www.heath.gwu.edu is an online clearinghouse on postsecondary education for individuals with disabilities. The site has a lot of great information including a great toolkit for counselors and advisors called Advising High School Students with Disabilities on Postsecondary Options in PDF format (note, chapter 29 focuses on financial aid).