When I desodered the RF box on my NESp, I sucked up as much soder as possible with my desodering iron. When I had gotten as much as I could, I used my sodering iron to heat up the remaining soder and used a flat head screwdriver to pry the RF box off of the board.
When prying, be sure not to pry the box too hard, because you may damage the board. I used a twisting motion once I got the tip of the screwdriver under the box. It worked great too

until I fried my screen.

Life is a lot like a video game without the extra lives and continues.