Who owns the instruction manual?
You retain all of your ownership rights in your content.
However, by submitting content to BrickLink, you are granting BrickLink the license to use, reproduce, modify, distribute, display, prepare derivitative works of, and perform the content in connection with the website and BrickLink's business as per the Terms of Service.
By not submitting an instruction manual, you give BrickLink the exclusive license to create, modify, and allow selling of works and instruction manuals in relation to your content. BrickLink can refuse instruction manual services at any time for any reason.