Smiling and growling are not one in the same. My Goldens smile a lot and wag their tail too. Dixie even "talks" (a low rumble from her throat that someone could take as a growl but isn't). It is her way of greeting. When I come home we go through a ritual of her "talking" for minutes and wagging her tail so hard her entire butt wiggles! My guess is this golden wants to play.

When the hair on a dogs back stands straight up, that is referred to as hackles.