The upper heating element is removed in the same way, although you don't need to remove any black plastic surround.

The disassembled items are shown in this image. There is no need to remove anything else for this repair unless you want to do a deeper clean and check wiring in hinge etc.

With a multimeter you can confirm that both elements have a resistance across the terminals of about 33 ohms. (Note the elements identification is for 115v because both are in series ie 230V across the two. The date is also stamped there.)

Check the resistance between a terminal and its metal sheathing (use abrasive paper to get a good connection if necessary). It should ideally be above about 2Mohms. My cheap multimeter did not give a steady value but rose from about 100kohms to 2Mohms over about 18 seconds (probably due to inherent capacity of 4-6uF).

The relatively low resistance to the earth sheathing was probably the cause of the RCD tripping. To solve this I heat-treated the elements in an oven at 150C for 1hr. After this the resistance to the earthed sheathing was satisfactorily off-scale ie above 2Mohm. (The capacitance had also halved).