Hmm.., I can tell you roughly how to do it. Just put both images on different layer and then use a mask to "cut out" the images so that u can place them together. If still blur, try to look for any good PS books in the library under the topic using masking. It's basically just that.
well...use the selection/feather function lor...feathering will help make the edges soft...select the areas where you want and apply a feather of say 20 pixels at the menu under Select...cut using standard Alt-X command...and then paste onto a new layer...simple as that...heh use this method to create montages for my wallpaper last time...heh
i still can't understand what you want to do....... hehe....... ;p
But if u mean like cutting a tree in one pict and pasting it into another pic of an empty grassland, then there are lots of ways to do it. Basically just mask out the tree then move it onto the other canvas and then adjust the curves after which you use a soft brush to merge the joints.......