If I am roasting the turkey in a convection oven, does that change the need to turn it over?

Yes, according to Cook's Illustrated, this is why you'd flip -- you get the rendering fat from the dark meat to flow down to baste the breast, then flip it over to finish browning and crisping the skin on the breast meat. But it should still be juicy and tender, even if you opt to skip this step.

I thought the turning was to let the fat from the bottom flow down to the breast meat and then turning it to finish by browning?

i've never flipped my turkey over---just baste it regularly. love the convection oven for this!

Interesting question -- it probably does help the air circulate around the bird (as long as it's on a roasting rack). Also, in his various articles about turkey, Russ Parsons has sounded pretty flexible about the flipping (he initially called for 2 more quarter flips to brown the sides, but got over it). So if you don't feel like doing it, don't worry about it!