Manually translating site and making it bilingual as well as other customization

Hi everyone,

I’m a first time user of WP/Studiopress themes and have basically zero knowledge of coding. (just basic understanding of what things mean). I’m using SP Magazine Theme. I’d be insanely thankful for every piece of help you might give me. Thank you in advance!

1. I need to create site in two languages: Latvian and Russian. Content and menus I’ll translate manually. But I’d need to translate things like dates, “Filed Under:”, “Return to top of page”, “Leave a comment”, “Edit”, “Reply” and etc. I’d like my sites’ address to look like this rus.casinofun.lv or casinofun.lv/ru for Russian version. (preferabbly 1st variant). What is the most effective thing to do to achieve these goals?

2. I’m planning to do customizations #1 as well as custom logo, tweaking a bit of css to adjust column width (how to?), custom social buttons for social networks that aren’t built-in any plugins (will jetpack work for this?) and some other things certainly will come up. Considering all this do I need to create a “magazine – child” theme to protect myself from losing everything when theme will be updated?

Any replies are greatly appreciated!

Regards,
Roman