Quick update hints for Mantis 1.0.x:

1) Change line 104 at config_defaults_inc.php:

$g_manual_url = 'http://manual.mantisbugtracker.com/';

2) Edit the file ./core/html_api.php to change the string 'mantisbt.org' with 'mantisbugtracker.com' on lines 291, 381 and 382

Hope it helps