Balu has no real pre coded standard so as is mentioned
It will be sufficient to replace the image of the logo in the header (while respecting their shape and size).
You will find logo PNG in the images folder of theme
Not possible using MM. (likely some browser refresh/cache clear maybe needed after change).
it is called from line 38 of layout_code php (layout code folder).So in case you do not have a png but jpg ok to change, but SAME size!!