Removing header entirely (so that the menu is on top of the background)

Hi there! I’m using Rock Star pro – love the theme in general but – I want to do two things I can’t quite figure out:

1 – I want to be able to remove the header entirely. As you can see, without a header image I’ve got the menu on top of a black background:

http://musicmanwilson.com/

I would rather that background shift up and have the menu on TOP of it – everything else I love. The way the menu/title shrink, etc. I just want to have all of that on TOP of the background. More like this site:

https://aarontrumm.com/

at least on first load – on that one, once you scroll, the menu has a black background, I’d like to keep it transparent so I can see the background.

2 – I would love to be able to give a page a different background…

I don’t mind CSS and coding – just having trouble digging around figuring out how to do this.

Thanks a bunch!