I've rebuilt a lot of these guys on older Hondas, and usually there is a little metal wire split ring that holds the rubber boot on (where the lever itself presses on the end of the piston.) After you get the boot off, there is an internal circlip that holds the piston assembly in the master body. It requires a set of long nose snap ring pliers to remove, usually (although I have managed it with 2 small awls, but it wasn't easy!) Depending on how stuck the piston assembly is, you can usually get it out by blowing compressed air in the fluid outlet hole (do it in a box with a rag covering the end of the master body, and keep your hand out of the way, the piston sometimes comes out with a great deal of force.) If it is really stuck in there, I have fitted a grease zerk in the fluid outlet hole and used a grease gun to "hydraulically) remove the piston. A rebuild kit should be available from honda that includes the rubber cups, springs, clips, etc that need replaced, (although if it is just sticking you may inspect the parts and determine they just need cleaned up) and you need to clean out the bore of the master and make sure that there isn't too much pitting (I've "honed" the inside of them using scotch brite pad to good effect.) You also have to make sure that the tiny hole(s) that go from the piston bore into the fluid resevoir are cleaned out and open (be careful, you don't want to enlarge them, just clean them out.) You can find an exploded view diagram of the master to see how it comes apart/goes together on www.crotchrocket.com
by going to the "OEM parts" lookup for your specific bike and looking at the diagram for the front brake master.
Now, all that being said, if you don't feel comfortable with all this, don't experiment! There isn't much more critical on a motorcycle than brakes, and doubly so if your "boss" is going to be riding it. If you have any doubts about your ability to do this, please get help or let a professional handle it. If you are half way handy with tools and do most of your own maintenance, though, you should be able to handle it. Good luck!