WordPress.org

Do I have to know about this Google API thing, or anything else techy?

You can get by with very little techyness, just WordPress custom fields and shortcodes. They're really not bad - look over the Usage section under Other Notes.

If you do want to get adventurous, you can have fancier charts in more places.

Can I skip learning to configure Tally Graph and just hire you to put charts on my site?

Sure, just send email to cyberhobo@cyberhobo.net.