1. To get a faded edge clone tool, expand the color wheel and dial down the transparency option. This trick doesn't work with brushes I'm afraid, but if you search you should find a plugin to let you use custom brushes.
2. I don't think you can clone from one layer to another, or from one image to another. It may be that the best you can do is to open a double wide image and paste the two images in side by side.
Hope this helps a little.
Also: http://www.getpaint.net/search.html
EDIT: Thanks for the fix BB.