Soo to answer your question instead of shitting all over you for actually asking a non-retarded one for a change (DAE BARM PLS HOW DO DUPE??)
Yes, you have to piece things together. Probably the best way to get started doing that is by simply updating the currently available scripts for the game (most of which are well commented). Update the easy ones first (AutoNexus, for instance) and move on to the more complicated ones (AutoAim, maybe?). They all have valuable things to give you a feel for the code and what some obfuscated class files persist over the course of multiple builds (ie, where you place the reconnect code is always going to have a different .class name, unlike Player.class, but it will always be about the same code).
If you're willing to suck a little dick, @
maat7043 (fuck idk the #s of the top of my head hope that's right) has a very beautifully done tool that can help clear up the junk code, although names will still be butchered.
ETA: "Bookmarks" will help you over the course of multiple builds. Find code / names that don't change and can serve as a "marker" on where something you're working on is between 20.0 and 20.1, etc etc. All of those _br / _aO will become something entirely new as soon as they push a new .swf, so don't get used to reading them as they are. The only ones that will persist are things like Player and normal plain text strings.
@
everyone else - I'm all for shitting on idiots. Its like, my favorite thing to do on MPGH.. But at least this guy can put together a full sentence and isn't asking anything wildly retarded. Cut him some slack, eh?