Replacing a rear main seal is really not that much of a deal.
You do have to drop the oil pan and pull the rear main bearing cap off , that allows access to half of the seal right there , you then need a tool that in my day was called a sneaky pete ,
it has a tool that looks like a cork screw that you screw into the top half of the seal then pull it out. Then you slide the other part of the tool through the seal cavity insert the new seal top half and pull it into place. It sounds a lot harder than it really is. If you are at all mechanical you can do it.
Good luck!!!