Practically and safety speaking, and although its a simple task in theory, its just not a good idea for such an inexpensive and critical part. I would agree with @KronoS on this.
I've tried something similar and found that most chargers are fused together (the two "plastic" parts) with either high temperature or glue. The only way to break the seam causes a very ugly edge that even if you are lucky to get a semi-clean fracture without causing a side fracture, will still look really sloppy when its glued back together.
Inside, there are mostly likely two large capacitors that would still hold a charge, regardless of how long its unplugged - because chargers contain switching circuits that aren't like an open faucet that can "run out".
So in theory, if you managed to cut this open without loosing any fingers, avoided the capacitors, you then most likely find that the AC cord needs to be resoldered back on. It should have a knot on the inside to prevent it from coming out of the charger case. (Underwriter's knot).
Take a look on ebay. You can get a replacement generic charger for about $10 with a 3 year warranty.
Speaking from experience, its just not worth the time and risk to bother hacking a semi-broken power charger.