Small turkey for practice
I like to practice too if it's something I've never made before. Roasting a chicken will give you an opportunity to practice the all-important skill of correctly placing the thermometer, but chicken has a different flavor than turkey.

One option is to get the smallest turkey you can find, experiment with a brine (which I highly recommend for roasted turkey) and perhaps go into Thanksgiving with a bit more confidence. 

You can always cut up the turkey meat and freeze it for sometime after Thanksgiving when you're no longer sick of turkey. Leftover turkey makes great tamales or enchiladas.