How does the OWC Professional Installation Service work?

I am thinking of sending in my Mac Mini to OWC because I'm not good with the insides of computers. I am wondering how the Service works. So am I suppose to add the Service, the RAM, and the Hard Drive to my basket and it knows what to do? When I get the box, do I go to a local FedEx facility to send it back? Is there anything else I need to know? I need advice from people who have sent in there Macs to OWC. Sorry if I sound like a noob, I am new to Macs and just wondering how the service works.