Look to see if "low first" award inventory is available on the USAirways website. If it is you can call in and use miles and co-pay.
Alternately, buy silver preferred and then you can use only miles and forego the copay.
If you don't have miles then this strategy obviously won't work.
Otherwise there's a near zero percent chance you will get upgraded on this flight because there will be enough preferred members to fill all the first class seats. It's possible there will be no shows I guess then they could sell F at the gate but pretty unlikely.