header problems, facebook like button

Hello! I am having some (hopefully small) Problems: 1. In the middle of my Header there is a black box with a White cross inside, indicating that there is some picture missing (sorry but I really dont know how you call that stuff). When I look at the proberties of this missing picture, I see this path: http://diabetesordination.at/wp-content/themes/catch-kathmandu/images/demo/header-image-1280x400.jpg. How can I get rid of this? 2. My logo is consisting of two elements: the logo itsself and one font. Both, logo and font, is one jpeg. I think for seo reasons it would be better that there is no jpeg but a normal font. Is it possible to change my logo into a font which Looks similar? 3. I would like to have a Facebook like it button which is very simple. This should be added to the footer in the social icons area. Can you recommend one plugin? I've tried a lot, but most of them seem to be too large with photos, etc. or they only can be used for posts, not for front page. please check my hp on diabetesordination.at Thanks very much!