197423 Server Admin/set up help ASAP

I have a AMD Athlon 64 X2 5600+ Dual Core, 4GB DDR2 RAM and 2x400 GB SATA II server that I need some help with. It is running a 64-bit Debian 4.0 min with Webmin (LAMP). I need someone who can make the server as secure as possible so that it is impossible (or as good as it gets) to hack. I also need something that can scan e-mails for spam/viruses). All the software that are going to be installed must be free. I also need help with setting up nameservers.