Audiovox model VOD715

I have a in car audiovox VOD715. I have lost the remote. I bought a RCA universal remote as per the audiovox operaters manual and programed it as I would a TV ( again as indicated in the manual). The RCA remote will only turn the unit on and off and adjust the volume. No other funtions operate. Have run the RCA remote thru the auto search and can't find a code to operate the other functions. All I really want to do is adjust the screen resolution but there is no way to do it without the remote. E mailed Audiovox and they would not help me with the universal remote problem and said i could buy a replacement for $50...rediculous thought they may have me....though their operatorss said i could use a universal remote...any ideas
Len