After you remove the alternator follow the oil cooler lines down with your hand to the thermostat block where they attach to the block. The bolt in the center will remove both lines from the block and then 4 e-torx bolts to remove the thermostat and replace the gasket.

I don't think anyone's done a DIY because there is no way to see the thermostat where it attaches to the block. You have to do all this by feel.