If your application is not using https then I would not recommend the use of that module.
Just have paypal handle the transaction https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/wp_standard_overview/
And make sure you check the amount paid when paypal postback to your meteor site to confirm the transaction.
Edit: Make a route for paypal to postback too. Paypal explains it here: https://developer.paypal.com/docs/classic/ipn/integration-guide/IPNIntro/
The route you make in meteor should check if the transaction amount and stuff like that is the same as the order you have. This is to make sure people don't mess with the form and pay less then they should.