nothing to it bro.
just take that little plastic thing off with a flat head screw driver.
undo the screws and put them somewhere so u dont lose them
cut the 2 wires (as close as possible to the speaker but not too close.. coz the wires arnt long so u will have more to play with)
wire the new speakers in. (black is always negative -) and positive + is mostly red but can be blue, grey ect.
use insulation tape where needed so something doesn't happen to short out
screw the new speaker in and your done.