What's the fastest way to fix stripped gear under warranty?

After four uses, our brand-new QQ-2 started making "burrrr" noises and slowly turning in circles. I noticed white plastic crumbs coming out of the left wheel base. I looked inside, and found the damage in the two plastic gears that drive the wheel. The worm gear stripped the teeth on the round gear. The cause looks to be a hair wrapped around the whee's axel, that got tangled up in the lubricant.
We just bought the QQ-2 a week ago, so it's still under warranty. What's the fastest way to fix this? I don't want to ship the whole robot, and I wouldn't have a problem replacing the wheel myself.

Thank you!

Boris