A ton.
Regardless of what some people think, you can't just have some all world player at any position and not game plan for them, but they still go off come GameDay.
I'm not going to get into the specifics of how he changed his offense to suit Lamar's talents, but he did. He couldn't run what he was used to with a LaFore or Brohm at the helm, he had to change it up.
Lamar though was better than the parts that surrounded him. His OL, it was okay at best. WR's, same thing. He designed the offense to create space so that if something broke down, Lamar could use his wheels to get yards. Eventually teams would have a spy on him, still one on one he'd get results consistently.
An example is if you put Lamar on our team last year, he would've looked human. Don't get me wrong, Lamar bailed the offense out a lot, but not from a schematic POV, but from a player breakdown role.
Petrino will be a good OC at A&M. Will he be cutting edge, it's hard to say. I wouldn't put it past him, but one trend I've seen countless times with aging coaches is that they tend to go with what they know rather than put in the work they would've at a younger age. How much does he have left in the tank? He's got the talent, although I don't know their QB state, so there shouldn't be any excuses.