1. Yes service dogs are allowed in most colleges, even in the class.
2. You will generally have three types of classes depending on the degree you are doing, these are the classes:
Lecture: This is what you see when you look at videos of college. A lecture is usually a large room with a lot of students, for subjects such as first year mathematics there can be over a thousand students, so it may be a bit worrying for you. It's good to try and sit at the front perhaps and focus primarily on the board so you don't think about the other people but if that's impossible there are other solutions. For one, lectures are usually recorded, either via voice or video-voice, in this case you can literally download the lecture from a computer and get pretty much the same experience as you would in the lecture. Lectures are not hand-on experiences, it's simply a lecturer talking at you and maybe doing some drawing on the whiteboard, if the recording is audio only you obviously won't be able to see the whiteboard. You may also be able to get note-takers to actual record the lecture notes for you or the professor himself may hand out lecture notes. Lectures are primarily optional and you do not need to attend the lectures, though some lectures are mandatory.
Tutorial: Tutorials are made up of much smaller classes of maybe 10 to 15 students. In a tutorial they usually go over what happened in the lecture and these are usually mandatory. Though the class size is much smaller so you it will be easier to cope with. Unfortunately, on many projects, you will have to work with other students, but it's a good experience and can help you grow if you see it as such. Tutorials are more like your high school classes
Lab: Labs are only applicable for engineering/science degrees, so if you aren't doing a degree like that you won't have a lab. Labs are exactly what you'd expect them to be, hand-on lab work, so doing experiments and what not, I assume in groups. So you will probably be working with other students but again that can help you grow.
Again, I haven't been in to Uni yet, so this is all what others have told me and if I'm wrong anyone who has been to college correct me. Generally, I think the thing you'll have most trouble with is the lecture but that's not a problem because they're optional and there are alternate means to get the same experience.