To change "Ask a Question" to "Need Help/ Post a Query" you need to set up your custom language:
1) create your lang folder (e.g. en_CU) in /qa-lang/ .
2) copy into it all files qa_lang_*.php from /qa-include/ folder.
3) edit qa_lang_main.php : 'nav_ask' => 'Need Help',
4) Occacionally, edit qa_config.php :
'ask' => 'needhelp',
If you want to add a box with a link on a question form, you need to write a plugin. However, more easily, you can add a custom html on the top of question form with some description that user is likely to add some referring URL within his question. Because why hide the url beside a button ?