Mike, the tires that come with the trainer are decent so I wouldn't worry about replacing them.

As for the wing, the dihedral is already set so I wouldn't try pulling the dihedral out of it, not worth the hassle.The best way to do that is to build a kit, or you might want to buy a wing kit like for the Great Planes PT 40 and fit it to the Tower Trainer.

My recommendation would be to get a kit like the Sig Kavalier which is a shoulder wing which would make a good second plane, but with a kit you will have to buy everything for it: tires, fuel tank, covering, motor mounts.