2. Read manual again, with camera at your side so you can fiddle with it while reading the manual.
3. Read the manual.
4. Configure the camera.
5. Hit on your friends, spouse, kids, relatives, etc., to pose for both handheld and tripod portrait shots in natural light. Whatever your favorite shutter speed used to be when using the D200, double it when using the D7100. Use an 85mm or longer focal length, but pick one lens and use it for every portrait shot so you can get a feel for how well it does on the D7100.
6. Review all the photos on a calibrated monitor. Adjust your shooting technique as required, based on the conclusions of your review.
7. Find a local wildlife or conservation area, and go for a couple of walks with specific subjects in mind. Pick one zoom lens and use it exclusively for each walk so can get a feel for how well it does on the D7100.
8. Review all the photos on a calibrated monitor. Adjust your shooting technique as required, based on the conclusions of your review.
9. Refer to the manual for configuration changes as needed based on both reviews of your photos.
11. IMO, forget about shots of brick walls and clear sky shots at f/22 and high ISO shots with the lens cap on and shots at 1/15s of your socks lying on the floor under the dim, yellow light of a 25W table lamp. I can find a performance or photo problem with every camera ever made if I push them hard enough, but those aren't real photos - they're merely ways to show that the camera designers didn't develop a camera to be used in absurdly difficult or pointless conditions. That is not news.
12. If you're not fully confident with the D7100 during the week prior to your departure date, don't travel with it. Having to fiddle with somewhat unfamiliar control positions and menu items is not an ideal situation when you're on vacation. Take the D200 instead. The best camera to have is the one you know best, or the new one with which you've made yourself confident enough.
13. Did I mention that it's strongly advisable to read the manual several times?
14. Follow this simple process and four things will happen. First, you'll end up with some great portrait, landscape and wildlife shots. Second, you'll quickly become familiar and comfortable with the camera. Third, you'll develop a good idea of the range of conditions and exposures in which the camera performs best. Fourth, you'll quickly discover any problems.