upgrade question LAX-MEL

Hey all

Hope you can advise on this one.

My travel was abysmal last year so only gold status now.

I need to travel LAX - Mel for work and trying to figure out some rules....

If I buy a M ticket and want to upgrade to business.. whats the price in either cash or miles.

Also, if I book a M ticket... who has higher priority... me with the M ticket or the other guy with a discount ticket but higher status like platinum or higher?

Hope someone can advise.