1) Report this agent to the Better Business Bureau, as well as to the American Society of Travel Agents and Holland America. Their "customer service" skills are severely lacking, which is a shame.
2) When you get to the dock, bring along some preprinted labels (Avery 10 per page should do nicely) with your name, address and cabin number on them - you can pick these up in any computer store and Word templates are readily available at the Avery web site. Then just stick them on the tags, and you're ready to go in a few seconds.
Hope this helps, and all the best of luck to you!