as far as breaking a computer goes physically its quite hard to do as long as you dont force things. if something is ment to go in to that slot it will fit there with only a tiny bit of pushing, dont force anything and you will be fine...
i would suggest you first confirm that you have got 2 wireless network cards in you pc (anyone on the forums could tell you if you take a pic of the inside of the pc). if you have take one out. its easy to do just unscrew the screw holding it down (inside the pc on the back wall see image only remove the screw above the card you want to take out not the blanking plate). and it then just pulls up and away from the motherboard (big flat board with everything sticking up from it).