For focus? Set up the shot, figure out where you want to stand, place the tripod without the camera, stand where you want to stand and then focus on the tripod, your camera is now focused for that distance and you can set it on the tripod. I use that reverse focus trick when I hand my camera to people to take my photo with it, I remind them to NOT change the focus as I have already set it for them. If you don't trust yourself to not bump the focus, you can stand something where you want to stand and focus on it. Lastly, you can use the distance ring on the lens to set focus and then use a tape measure to get into position, that is still how they focus film movie cameras, and why actors have to hit their "mark" it is the focus point. When using this last method if you want shallow dof, you need to remember that focus is to the film plane indicated on the camera by something that looks like this ---O---.

As for snapping the shot, if your camera will accept a cable release, (I'm not familiar with your particular Nikon) you can use a squeeze bulb with your foot, or a screw on timer, or the Kodak cable and timer contraption. I use the Kodak timer and cable set up and it does work quite well. Or do you have a built in timer?

Good luck, let us know what worked for you.