Just like the title says I am thinking about replacing my 03 Yamaha YZ450F Engine. Yes the entire engine, top and bottom, went blah on me. And I have a few questions: 1) Should I: - replace the engine - part out the bike - or sell it as is? 2) What is the cost range for another engine? 3) What year range of an engine can I put in mine? 4) Does anybody have any suggestions on where I might get an engine? 5) How much is my bike worth right now? Thanks in advance!