How do I safely dismantle Brother KH840 Carriage?

I have a Brother KH840 just purchased
The carriage is jammed Control ok N-L then KC
But KC to SM jammed and off course cant get to CR

It appears gummed up sticky etc.

If I knew which screws to remove top plastic cover I could look further and possibly clean mechanism and free it up I just want to view the working parts from the top down with the cover removed
any help appreciated
Thanks
Ian