I was a prior rated (Nav) SRO and can tell you that it can definitely have an advantage for your class if you do your job right.
First rule... Being the SRO is about the class, not you! It was said before, but wear the Wings you have already earned if your are prior rated... aside from that you are just another fucking student. We had a few prior rated/aircrew (both O's and E's) in our class and my first rule to them was to put your leather jacket in the closet and don't take it back out until you are UPT complete (they agreed as a group on this). To be honest, it was actually kind of a cool goal for that small group of us to want to wear our leather jackets again and at the same time it was a message sent to both the IPs and the other folks in the class that we were all the same. The Flight CC actually told me it was perfectly OK for us to wear them, but I told him we decided not to as a group.
Behind closed doors with the Flight CC and/or prior MWS IPs you will most likely have the advantage of being a "crew dawg" and you can use that to your class' advantage, but don't ever put any instructor (especially your Flight CC) in a position where they think even for a second they need to take you down a peg in front of other students. Treat your FAIPs with just as much respect as you would a prior MWS IP and let the rest of your class see that... make it obvious! I actually knew a few of the IPs in my Flight from my prior airframe... I helped carry my Flight CC out of the Brit Club in Diego hammered once or twice and remember the Q-3 the Asst Flight CC got for trying to fly over a thunderstorm a few years prior. They are human, just like the rest of us, but you'd better know the difference between the guy you are talking to with the door closed in the office and the Flight CC addressing your class. They are two very different people... treat them accordingly.
Arrange study groups, stomp out any gouge hording, plan weekend class activities that can include everyone... to include those with wives and kids (BBQ at someone's house, camping, waterskiing/tubing on the lake), know who is doing well in the class and who isn't (and know why), stomp on your class before your IPs have to if things even get the hint of going sideways for any reason. Bottom line is to take care of your folks and don't try to hide anything from your Flight CC/IPs... the walls are very thin between the flight room and the IP office and they are never not listening; if something is going on with anyone in the class the IPs already know about it... trust me!
Finally... take care of yourself as a student. Study as hard as you can and be a good classmate. The Flight Commander has enough say in T-6's that he/she can put almost anyone in the top 2/3 of the class flying wise in the top 3 overall at the end of any phase. Someone will finish first and someone will finish last... do the best you can to help ensure that everyone finishes (most importantly, you). If as an SRO you take care of your class (and your IPs) and you finish out well you will most likely end up flying something you are happy with (hopefully one of your top choices)... and you'll look back at UPT as a lot more fun than you remembered while you were actually there!