I use CS and Elements 5.

In either I would use the MAGIC WAND.

1. Select MAGIC WAND from the tool box.
2. Make the tolerance 32 to start with. (You can change this up/down depending on the accuracy of selection.)
3. Place the MAGIC WAND into the grey and click. This should give you marching ants around the grey.
4. Open the image you want to put into the grey.
5. Copy the image to the clipboard.
6. Return to the "grey area" and EDIT>PASTE or PASTE INTO.

Now it gets tricky as to sizing the image to fit the grey.

Another way would be to put the template on a transparency layer.

Then you could use the MAGIC WAND to select the grey and cut it out. Next to put your image between the template and transparency and size to fit using TRANSFORM.

NOTE: SAVE often!