To implement time and payroll will required resources, experiences, and knowledge or else your project will failed. Some of the key elements are payroll infotypes like PA0008, PA0009, PA0014, PA0015, the tax infotypes, payroll schemas. Time configuration is a project in itself.
I would suggest your organization to work with the major consultant firms for a successful implementation. Even working with Platinum consultants, there are still a chance of your project being derailed.