To actually answer your questions you need to understand that all the text you see on your site comes from either a constant in a file (this is the language pack containing loads of files with generic text strings) or the product/category descriptions you have entered that are stored in the database.

ZC comes with english constants/files.
To add another language you add a language pack which means copying another bunch of files into your site that have the same generic texts in them as the english files but in the new language.
Then you tell ZC these new language files exist. At this precise moment ALL the product and category descriptions YOU have added into the database are duplicated (obviously in english) to be used in conjunction with the new language pack when selected by the customer. YOU now have to translate all those descriptions into the new language.
Now either you can offer english AND the new language, OR force only the new language to be offered to the customer.

So now you see there is no "conversion" at all. It is duplication and the languages exist in parallel.

As for administering a site in a language you do not speak, well you need to have a pet translator.
You add your new product in english then poke them to translate it into the new language as you need.
The order confirmation emails go out in the language as selected by the customer anyway.
You can answer direct queries using google translate and copy and pasting. A couple of our suppliers do that, it adds some smiles to the day with the gibberish it comes out with, but we get there in the end.