Where do I start?

Wow! Good luck, which will come from good planning. I would find a local Doc that is knowledgable in Occ Health. You want one that will work with you and your company. Obviously the AAOHN site will be a good place to obtain info. You may have to get into OSHA requirements based upon company size also. As far as working as a OHN as a LPN, check with state board. I know some states specifically disallow it without RN supervision on site. Work with your company's insurance carrier, they should be able to provide some help also with regards to documentation and on site requirments.
Keep us advised,