There should be a maintenance manual within your owners manual. If it isn't, search the mbusa website. It is probably downloadable there. I remember downloading the entire maintainence manual for my '07 GL 320 there. That manual will NOT be enough to enable you to do your own work but it will get you started.

It would be interesting to know if they are withholding the information. I just went through this with VW - warranty compliance requires oil changes from VW approved oils list. But the list doesn't come with the car. So who has the list? Nobody has it. Dealers don't have it - "call VW NA". VW NA doesn't have it - "call your dealer". Ponzy schemes.