Unfortunately, you will probably need to put this into that manual.
http://web14.compaq.com/falco/detail.asp?FAQnum=FAQ2859
I would say that in general a firewall would be good to recommend, but the setup is usually too difficult for many users.
Also i have to recommend that they need to know how to use e-mail.. i.e. do NOT open/run everything that gets sent to you in e-mail, even if it is from a "friend".... too many bad things can happen.