(try not to use the erase tool because when you do you'll inevitably wish you could backup... 5 miutes ago... doh!)
layer mask 1st
then magnifying the pic to "draw" away the edges is tedious but
you can learn a lot about drawing and you may see something in that level of detail
that you may or may not have noticed before
in zoom mode you often get a better understanding of which colors in your image can be used to make edges stand out or blend into the replacment background
although sometimes you can get so fixated on some minute detail that disappears when you go back down to normal size that you wonder why you spent the time...but
bottom line
hopefully you have fun with what you are working on!