Something like sticky menus should be trivial for any web dev: find the menu you want to make sticky in the web inspector. Modify the styles inline until you make it work. Grep the theme for the selector that you modified. Copy your modifications.
I think that really illustrates Wordpress' versatility.
By that same extension, a custom hacked up theme is the "return 4; /*" of site maintenance.
By using a plugin, the person that follows you doesn't have to be a webdev who could float a css div blindfolded.
As part 2 will detail, the whole purpose of switching to Wordpress was to reduce the work load of building/maintaining the site. I fully agree, Wordpress is swimming in tutorials, docs, and sometimes guides disguised as advertisements for a paid theme.
Re. changing fonts - My actual first thought was 'Surely I just need to find the settings in WP that let's me change the theme's font', and my experience was that Wordpress did not 'natively' support this.