Martin,
I know it is scary. You likely wonder, will the work be much more intense then undergrad and maybe if you can do grad school and work at the same time. I understand.
I took some grad school classes before being thrust back into the work force full time. Now, I have applied to grad school to work on a masters. I plan on taking 2 classes per semster, but still I worry because everything takes me longer than it takes people without learning difficulties. However, I know that I did well in undergrad and in the grad level classes I took before. It will be difficult... but I can do it.
You have a few things going for you, including having meds to help your ADHD (no such meds for some LD's). You already went through college, so you have learned how to study in a way that fits your needs. Look for a grad school that fits your needs, in a school that has accomodations (like testing in a quiet place free of destractions, if you need it). I recommend a school with semesters instead of quarters, due to pacing issues.
I wish you success.
"Never give up, never surrender" -Galaxy Quest
“In the middle of difficulty lies opportunity” -Albert Einstein
“Be not afraid of growing slowly;
Be afraid only of standing still”
-Chinese proverb