Medical bills, lost wages, and possibly future wages based on the nature and extent of your disability. Now you're are talking about permanent disability. This is very case-specific. Your employer or state employment office should provide you with a copy. It wouldn't hurt.
Some unions have workers' comp representatives.
While they are not lawyers, they are familiar with the procedures and can help you avoid traps for the unwary. The whole point of worker's comp is to remove these claims from the court system and protect workers with a dedicated state compensation fund. Generally yes, but you have to go through exhaustive administrative procedures first, and possibly a trial before an administrative law judge, before you can take your case to superior court.