Not sure re Mk3, think mine is a MkII. General procedure for all single unit 200 series that I own is:

1- Remove underside two screws that secure front display section
2- slide out display section
3- remove top section screws from rear of unit that holds top section
4- slide off two clips at front that hold top section and lower section together
5- lift off top section.

You should be inside the 201 now.

Hope this helps.

John

808v6, M60, MC200, HD621, Lumagen XE, 504, SB Touch, 563, 201, 204, 208, MPMAX 221, M80, Explorer, Explorer2.