I would make an adjustment layer, make adjustments on it, then use the eraser brush on the area I don’t want to change. I have version 7, don’t know about elements. Can you make layers>
....when I had the original PS I used to make a copy to work off of.....*smiles*...I learned the hard way. I can’t help you now..sorry
I would try selecting the area you want to alter, go CTL-J to jump the area to a new layer, and then make your alterations on the new layer.
Swamps gave good advice. Also, when I finish and line it up from layer 2 over the original layer, I put on a temporary 50% opacity so I can be sure it’s perfect, then I turn off the opacity. Also, depending on what the subject matter is, I put a soft layer drop shadow on it which can help blend it a bit. Then make a “save as web” so that you can see it in preview and not accidentally flatten your psd file. You can see something I just did this to at YouTube by searching tiger woods roaring success radio hour.