Without getting into layer masks, here's my dummies way to to this:
Open your colored image in Elements.
Go to the layer palette and drag the background layer down to the new layer icon and make a duplicate layer. Do this once more for a second duplicate layer.
Click on the first duplicate layer (just above the background) to make it active. Go to Enhance/Adjust Color/Remove Color. Your middle layer is now black and white
Click on the top layer (second duplicate) to make it active. Click on the Selection Brush (3rd icon down on the left side of the tool box and have it in selection mode (look at the top menu bar). Select the area you want to become black and white. Hold down the alt key if you need to remove something you selected and draw to fix it. It will subtract from the selection. When you are satisfied that your selection is as good as possible (zoom in on difficult areas and use the bracket keys to make the brush smaller and larger to fit) go to Select/Feather and enter 1 pixel and click OK. Go to Edit/Clear and it should remove all the color from that selection. By the way, I clicked on the black and white layer and use gaussian blur (filter/blur/Gaussian Blur...use slider to your taste) to blur the b/w background.