ahh, ty for answering questions while i wasn't here ^^
i was trying to hook up a wireless router which was being a bitch and finally got it up ..
idk if it's working on the other computer yet but atleast i got my connection back

but yes, pen tool is overall best for getting ..the best curves around edges w/ ease.
and i believe you have white edges because you didn't make a new layer under the wallpaper before you deleted the selection.
just practice with the pen tool on rendering and soon, i am sure, it will be your best friend ^^