You will need a crank extractor, one with some kind of ISIS adaptor - it's usually an indended cylinder shape. Like this.
Then you will need a BB tool - Like this.
Then you pull the cranks off with the first tool, undo the BB with the second tool, then put in the new BB with the second tool and slot your cranks on and do them up.
Remember that BB shells have opposite threads on one side. I forget which side, though. Someone else is likely to post after me saying which.
Boo, snaked.
Edit: The reason I mention BB tools is because truvativ may well have made the splines on that BB a different shape. Their old howitzer system is an example. It looks like ISIS, but it isn't ISIS, the dicks.