cut around the object using the lasso tool, ( this does not have to be fantastic ). When the dotted line appears go to edit and then copy.
Click onto the image you want to paste into and then click paste. The image will now be on a layer. If the size is wrong you will have to delete layer go back to the original pic and change image size.
if the size is right, you can drag the pic into position and then delete around the layered image using the rubber tool. You can use all sorts of 'brushes' for this.
So, rather than trying to 'cut' perfectly around an image, you copy/pste the image roughly and then 'rub-out' around it, giving you much more control.
Now that this image is on a 'layer' you can make all sorts of adjustments to it ie: colour balance, lightness, contrast etc.