Terence,
If you just changed the text on the fields, that shouldn't be a problem at all. If you changed the functionality in the PHP, that could be an issue, but it'd be impossible to know.
As for custom fields, JFBConnect is able to import Facebook profile information into any text, textfield, date (mainly for birthday), or URL type fields. Other fields such as select, radio or 'choice' type fields can't be imported into from Facebook. Almost all data from Facebook is free-form input from the user, so it's not possible to 'match' that input up to specific selection options that you may have created.
Hope that explains, but if you have any other questions, just let us know. Additionally, all of our extensions have a 30-day money back guarantee. So, should you run into issues you can't overcome, you can easily get your money back.
Hope that helps!
Alex