Please don't PM me to ask for help or to join your mod development team. Asking your question in a public thread preserves it for people who are having the same problem in the future. I'm not interested in developing mods with people.
Yeah, you do in fact have to rewrite some portion of the mod. Like Choonster says, your IDE should help you understand what needs to be changed. However, it isn't always obvious what to change to as some concepts like block states is a major change.