I have a co-worker who was in a situation similar to yours. I believe he's nearing 30 now, but basically, he was unemployed for quite some time (something like 4-6 years i believe) and that was more or less because of problems with his shoulder (an injury of some sort)
Our work environment is a kitchen so you can imagine how straining that would be on him, but he's always had a positive outlook on the whole thing and tries hard. Because of how much effort he puts in, our Chef keeps him around and is flexible on how often he's scheduled.
In your situation, I'm pretty certain you can do well with some determination and try to not worry about the pain too much.
In regards to school, even tho you've been away from it all for a while and you feel like you've forgotten, you'd be surprised at how fast you'll remember everything just by taking a look at the work infront of you.
Good luck with the interview tomorrow, and don't give up!
Keep us posted