While some people will find registering for health insurance as easy as booking a flight online, vast numbers who are confused by the myriad choices will need to sit down with someone who can walk them through the process.

Enter the “navigators,” an enormous new workforce of helpers required under the law. In large measure, the success of the law and its overriding aim of making sure that virtually all Americans have health insurance depends on these people. But the challenge of hiring and paying for a new class of workers is immense and is one of the most pressing issues as the Obama administration and state governments implement the law.

Tens of thousands of workers will be needed — California alone plans to certify 21,000 helpers — with the tab likely to run in the hundreds of millions of dollars. …

Over the short term, some workers may be funded by federal grants, state budgets or private money. But over the longer term, most of the costs are to be covered by the new health-care marketplaces, called “exchanges,” being set up in every state. The money will come from fees that insurers will pay to sell their plans on the exchanges.