Learning disabilities - yes, most post-secondaries have programs (it could be as simple as provding you with a copy of the professor's lecture notes, it could be having someone write for you as you dictate). But you will need proof from the professionals you see about your issues.

Preparing for coursework - I DO believe you can prepare for this. There are self-tutoring programs and workbooks out there for everything from math to English. I suggest practicing your writing too (maybe a timed paper weekly). Don't wait but immerse yourself as soon as possible in the subjects that concern you most.

Anxiety - Practising as per above will help your anxiety a great deal.

Auditing Classes - Can you audit (sit in on) any of these courses this year? The local university here allows it. In some cases you do however need the permission of the instructor though. Some colleges/universities allow this for free. I recommend this greatly.