Problems with My Account and adding Credit Card processing

[nakadude]

Just acquired this website from a someone who seems to have dropped off the face of the earth (lucky me!) .

I added a test account to my website and when I tried to login I get the following:
Warning: Cannot modify header information - headers already sent by (output started at /home/ballgame/public_html/catalog/includes/languages/english.php:337) in /home/ballgame/public_html/catalog/includes/functions/general.php on line 29

Not sure what to modify here to fix this one.

Even more stunning is that when I try to add the credit card processing module, I get:
Forbidden
You don't have permission to access /catalog/admin/modules.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/1.3.33 Server at www.ballgamememories.com Port 80

All the other processing modules are fine. Sadly, I can't get any information out of the seller so if anybody has some ideas, I'd appreciate it!