No. Pet aura talents were changed a bit in the update last spring. Now they will not replace an active, but you can replace an aura cast by a pet. It's quite nice. Amp is a useful talent, as it tends to cast in the rounds while you are buffing up for a big hit. Best of luck with your pet!
Yes. All aura spells are like that; none can be stacked and none can be used without canceling out a previously cast one.
That is all true, but doesn't answer the OP's question. You pet will not cast amplify or any aura while you have an aura active. If you cast an aura it will replace one the pet cast, but the pet won't replace yours.