By "hacking" into botnets I assume you mean getting into a pass protected channel where the bots are reporting to? How hard it would be to do this depends on the ********* capabilities of whoever created the bot. First thing you have to do is get the actual piece of malware that is being sent out to people. Sometimes just from viewing the executable in a hex editor you can see the plaintext irc server, channel, and password stored in it, but most of the time it is slightly harder than that. What you have to do is find an old computer you have NOTHING important or personal stored on, and possibly limit it's bandwidth somehow to prevent any DoS attacks from your computer. Then, place the malware (the irc bot) on it and execute it, while you are also running a packet sniffer. Then you will see the server, channel and password it is connecting to. Of course, if the bot uses encryption then it is a lot harder to figure out what is happening. Then, once you have the server, channel and password, you could join and change your name to one that is similar to other bots, so they think you ARE a bot, allowing you to monitor the channel for a while before taking it down however you feel necessary, and you could steal the bots and redirect them to your own channel.
Who needs drugs when you have electrons?