My wording was poor. I CAN get into the CP for the hosting account. I CANNOT get into the WP-admin area, since the logon name and password which I have successfully used in the past no longer seem to work.
I've found the "bad" Index.php in what the host labels the "public_html" area. I have backups showing a few different versions of other Index.php files:
a) in public_html/wp-content :
// Silence is golden.
b) in a backup folder :
* Dashboard Administration Screen
* @package WordPress
* @subpackage Administration
/** Load WordPress Bootstrap */
c) in the live "www" folder :
...the hacked index.php file
I know just enough to be dangerous. Is one of the "a)" or "b)" files the one I should copy into the "www" folder to replace the hacked index.php?
AND, what can I do about the WordPress ACCOUNT which seems to have been changed so that I cannot log in?