2 (hopefully minor) changes to Ambiance Pro?

Hey there!

I'm using Ambiance Pro for the first time, and while I love its look and feel, I'd love to make a few small tweaks to it. Can anyone help me:

1) Remove the default navigation bar option - Ideally I'd like to just have my menu links display without the visitor having to click on the menu icon. Is there a way to just have the links appear by default like most other websites?

2) Add a transparent image into the site header - I'm not a huge fan of the default gray that comes with the theme, and I'm still mulling whether to just change the background color or if I'd like to put a transparent image behind the header. Just to test, I did try to add a background-image property to the .site-header class, though, and it didn't work. In theory, how could I adjust the site header for an image? Or is there a non-site header alternative that I could do?

Thanks so much for the help with this! Apologies if these are relatively amateurish questions.. that's what I am!