My thought was to shoot the facing mountain side an hour or so before sunset to get the proper exposure. Not sure this makes sense.
That's the whole point of bracketing exposures.
In one exposure you will get the shadow detail, in another you will get highlight detail, and so on. If you're experimenting then shoot at least 5 exposures varying 1 stop each. use a tripod and do not move the camera at all. Use your exposure compensation button on your d3100 to change exposures by 1 stop. Start with 0, then go -1 -2 then +1 and +2.
Then take a look at your imageson youyr computer and see which ones would be best to combine for an HDR image.
Sometimes you need all 5, and sometimes 3 is enough.
Use a strong de-ghosting methond in what ever software you will be using.
Also, this is very important. Do not change any other settings between shots except exposure compensation. Also use the same focus point for each shot.