I see that paycheck JEs are for integration purposes and require payroll items for use. But, I'm not seeing payroll items in my account, which is not provisioned for payroll. Would I have to pay for payroll to enable payroll items so that I can then integrate with my real payroll system?

No. Just create a regular Journal Entry via your integration. There is no need to create a paycheck JE. I'm guessing you're just looking for the debits and credits (with proper segmentation) to come over from your payroll system, likely in bulk/summary format, and not full individual paycheck data.