Customizing Dashboard Menu (left side)

I have been searching without too much success on how to do some simple tasks via the dashboard.

I’d like to be able to have a section in the admin area that would allow a user to upload a logo and it would be placed in a “logo” section in the header.

Same thing with a banner area. I’d like to make it easy for admins to just click upload and place a banner in without having to do a lot of the back end stuff.

Hope that makes sense.