Ok. Can you give an example of how I would use urlencode() ?

Here you go.
php.net/manual/en/function.urlencode.php

You can use it directly on the alias of the extrafield.

I saw this www.joomlaworks.net/forum/k2-en/43118-clickable-author-link-in-article-view#147959

Is this another option?

I had completely forgotten about this one.
This is a bit different. You need multiple fields, but the method is the same.
You need to echo the value of each field like mentioned in that post separately (like the code mentioned there).

Another trick would be to create predefined lists of authors (select boxes) in order to avoid user error.

As for the attachments can you send me FTP and Joomla! so I can look into it?