Well, you are going to have to bleed the system, so thats a good thing kinda.
1) Drain brake system- do not get brake fluid on anything- you'll regret it, or wash it off quick.
2) remove the banjo bolt from the master cylinder. You may want to have a hose or bucket of water around, see 1 above.
3) You can remove the brake lever if you haven't already.
4) Remove old MC- 2 8mm bolt and the bracket will come off.
5) Install new MC
6) Put the banjo bolt back in(you should use new copper washers)
7) Put in fluid
8) Bleed system- use caution
Any problems, we're here to help.