Use your fingers or something else to put some pressure on the wrench and the nut, so you don’t tear it.

The nut is quite flat, but you can open it with a 14mm wrench when you angle the wrench so it fits between the openings in the group case.

Put the coffee machine in the back or if you can remove the bean collector, on the top.

Remember to empty the water canister, the spill collectors. Turn off your machine and disconnect it from power.

You don't need to open the machine for replacing the seal.