Customizing WooCommerce checkout page

Hello all!

I’d like some help with customizing the functionality of my WooCommerce driven site. The link can be found here: https://seekoften.com/eCommerce/checkout

My question is,
What files / lines of code might I want to look at if I’d like to add another drop-down to the checkout form, and how do I go about adding items to the drop-down?

Also, if I’d like to change the wording of “select a state” to be “select a province” ?

And finally, how can I size the product thumbnails differently than the size shown on the checkout page ? ( I want the product thumbs to be square, and the ones on the checkout page to remain vertically oriented ).

I hope you can offer me some insight on the topic, as I’ve searched far and wide, and can’t accomplish this on my own.

Thanks in advance,

Sincerely,

Chris “Fawkz” Coffin