Hi and welcome to mightyram. Be prepared for the worst when pulling the engine apart. It might need a trip through a machine shop depending on what has caused the engine to lock up. There is a ton of info on site for tips and tricks so be prepared to do a lot of clicking and reading! The most trouble you will get out of the engine will be the Mikuni carb. Tricky to diagnose and work on - but there's always the option of swapping it for something better.
Post pics, ask questions!