I'm not sure why you would want to comment out NLS_LANG; I don't think having it set will hurt anything, as long as it is set accurately.
To fix the date, you'll need to do one of two things.
You can set it from within Oracle, which is the best way to do it. Previous to 9i this was easy to do; just add it to the end of the init.ora file. However if your 9i instance is using an spfile instead of an init.ora file, which is the default, you can't do that anymore. I know values like this can be set via OEM, which we don't use, and I was too rushed at the time I did our Oracle upgrade to take the time to figure out how to do that without OEM.
So I used option two, which is to have them set in the environment for the user that runs AOLserver. In my case I set both NLS_LANG and NLS_DATE_FORMAT in the Daemontools run script for each site that needs it. You probably also have a wrapper script in $AOLSERVER/bin to set other Oracle-related environment variables and you could set it there as well.
After putting these in the right file, just restarting AOLserver should do the trick.
