I don't really get the question, on the one hand you want an easy solution and on the other you say you'll use the checkin desk.

The best way to checkin is to use the website *using you EC information or a website account). When you checkin you are also able to use the seat selection function. Another option (if you are e-ticketed) would be to use a self service checkin machine though I don't know if they are available at SYD, after the self service checkin you should be able to use a bagdrop desk.

An upgrade would be highly unlikely without status unless they start upgrading based on fareclass which imho doesn't usually happen, they usually go for status.