Hi...I am a travel agent so I am partital to booking with a travel agent. Travel agents can usually get better rates than if you book with the cruise line or at least the same. Don't ever pay brochure rates.
As far as insurance goes. I had some people that were from Spain and wanted to book a cruise through me. But since they were not U.S. citizens I couldn't get them insurance from the U.S.
I tried independent companies and you still had to be a U.S. citizen.
If you want to book with a U.S. travel agent and you want to get insurance you have to see if there is an independent insurance company in Canada that would just sell you insurance.
Travel agencies usually can sell just insurance without a cruise being booked. Thye should have insurance brochures.
I hope this helps.