Oik appears to be leaking from starter where it is bolted to the housing. Is this a pan gasket or rear seal problem? 3.0l v6 12 valve

 

It could be the oil pan gasket, the rear main seal or a valve cover gasket. You need to determine where it is coming from. Clean it off really good and have some dye added to it. You can buy a utlaviolet detection unit fairly cheaply and it is easily spotted when the dye comes out.