guardianship of child who is no longer a minor, but is disabled

[cyngbeld]

I am the mother of a 17 1/2 yr old daughter. She has Down Syndrome. Her IQ is less than 30, according to the school psychologist. She operates on the level of about 3 yr old. She receives SSI for her disability. My question is, do I need to go to court to be her guardian when she becomes 18, or do I just continue on as is? Do I need a lawyer to represent me if I have to go to court? I'm also on disability and don't have a large income.