there is no change required it works out of the box.
1. originate the transactions from the url provided with the CCAVENUE. for ex : if you have given the domain www.yourdomain.com, with CCAvenue then the working keys/access code & merchant id will work only for the transactions originates from www.yourdomain.com.
2.for some reason i am not able to get the transaction successful from the CCAvenue test server. But it works with the production server.