Merr. I'm a bit tired and there's a lot of explaining. Go search Github for custom Minecraft clients and dissect the code and understand how you connect to the server, build a packet handling foundation, etc,. Or read through the Minecraft code using MCP and build from that.
EDIT: If you haven't worked with RE'ing games/programs and/or handling a network, you probably won't succeed FYI.
EDIT #2: Minecraft system's aren't quite as complex as others I've encountered but with no prior knowledge, you won't succeed.