Custom header+background sections in MP Frontend

Hello! I am trying to build an etsy-like website(Gridmarket is the theme I am using), reading through the forums helped me a lot! However, I have a few questions I didn't find a proper response for(working for me):
1) I am using MP Frontend and Blog templates plugins because I want to limit the user's access for one and also provide him the same theme as the main one. How can I provide him the 'Custom header'+'Custom background' sections in the Frontend store so he can customize his store without entering wp-admin.

I have made a new tab along 'Products | Add new Product | Orders | -Customize your store- ' and would like to have the above mentioned options here.

2) Marketpress plugin- how can I enable Manual Payment for Global Cart?

Thank you!