Crop out your face and place it on the Mt. Rushmore pic as a new layer. Also make your face grayscale by removing the color and adjusting the levels to try and match it with the rock. You would probably want to add a little shade of red.
Create a new layer on top of that. Select the new blank layer.
Then select the clone stamp tool by clicking and holding the stamp tool icon. You should be able to select it from the popup menu.
To use the stamp tool, ALT+click to an area to select a pattern and then left click to paint over your face using your selected pattern.
I'd use different samples to paint in different parts of your face.
If the pattern is covering up your face, adjust the opacity of it in the Layers toolbox so it becomes partially transparent.
Using this method, I was able to make
this.
Sorry if my instruction seem a little vague. I use Photoshop Elements at home and PS 6.0 at work. I haven't used PS 7.0 in a few months.