There is no specific tool in Elements for choosing a range of colors like the Color Range selector in Photoshop. So, you need to create your own tool, which is surprisingly easy to do.
The Magic Wand tool has a setting called Tolerance, which defaults to a value of 32. You are not stuck with that value as it is a variable you can change to suit your needs. We can use this tool to select a range of values, and then modify the results. At the default setting of 32, if you click on a value of 200 in an image, the tool will select all the values from 168 to 232, or 32 values above and below your target. This is a hard selection in that value 168 will be fully selected and value 167 will be full unselected.
If we want to choose the highlight values in an image we can set the Tolerance of the tool to something like 80 and click on a very high value at or close to 255. This will select all values down to about 175 depending on the original target value, effectively selecting the highlights in the image. You could select shadow or mid-tone values in a similar fashion. If you click on a specific color, the selection will choose all the values within range for each of the three channels according to the values in each channel at the target point.
Now we can modify our selection in the usual manner with an adjustment layer whose mask will reflect our selection values. Your modifications in something like Levels will be rather harsh around the edges because of that hard selection of values I referred to, so we need to modify our results to make the process work for us without the funny appearance of the selected values against the unselected values. This is done by blurring the mask to effect a transition from selected to unselected areas. This blur in many cases will need to be rather large, so choose Filter | Gaussian Blur and drag the slider up until you see the modifications smooth out in the image.
Modifications like this work best if you overdo them to start with so they are easy to see, blur the mask, and reduce the adjustment layer opacity to control the amount of modification needed in the image. Painting on the mask with a soft brush or applying gradients from foreground to transparent will help you modify your selections to blend them into the original image.