Hi guys.. I am a newbie in Linux and now am facing this problem

The linux is redhat 7.3

our mailserver uses qmail, vpopmail, qmailadmin, vqadmin and sqwebmail.. i accidentally changed the logindomainlist file under /usr/local/share/sqwebmail and had it changed back to original content.. but the sqwebmail is not working. the apache error log shows 'premature end of script headers
/var/www/cgi-bin/sqwebmail' whenever i tried to access the page.. what should i do? i was suggested to re-install the sqwebmail. if this is the
only solution, can anybody provide me with detailed explanation on: 1. is it ok to install the new version, i don't know how to check the current
one's version, but it was installed in 2002, so it should be quite old.

2. How do i install it? should i uninstall the current one first? i have tried
to read the install.html, but given my low-level knowledge of linux stuff, i
don't really get it. can anybody pinpoint the important things i need to focus
from the install.html for the configuration and installation?

3.do i need to reinstall the others (qmail, vpopmail, qmailadmin, vqadmin)?

thank you very much in advance!! looking forward for answers soon.. =)

cheers,

pat