Hardy-har-har.

You need :
1. Money
2. a set of removal keys ( can usually find at Walmart )
3. an adapter harness ( one for a late model Volkswagen usually works )
4. an antenna adapter ( see #3 )

NOTE: If the new unit has 2v preamp outs, you will need to wire in the speaker outputs to the amp.
( This is assuming you have the Infinity amp - NOT a base model Crossfire )