Blogolife logo/header changes

I’ve read a few forum posts on how to change the header image in the theme

I followed the advice in the thread http://wordpress.org/support/topic/theme-blogolife-how-do-i-insert-my-logo-where-the-header-text-is?replies=31 and was able to upload a logo/header above the nav bar but it only appeared on the home page and not on any other pages (just showed a broken image link square).

Two questions:
1. Can I move the logo by adding this code in the header.php or do I have to add it to the css stylesheet too?

<img src=”full_url_of_image” width=”image_width_in_pixels” height=”image_height_in_pixels” alt=”alternative_text_for_image” />

2. Will it affect SEO if I move the header/logo above the nav bar and don’t use the Site Title and Site Description?

Many thanks
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