A good start is to go to the major AV sites and read what they have to say:
NAI (Network Associates)
They have tutorials on viruses and you can look at the analyses in their virus libraries to see how they work in practice.
If you cannot do someone any good: don't do them any harm....
As long as you did this to one of these, the least of my little ones............you did it unto Me.
What profiteth a man if he gains the entire World at the expense of his immortal soul?
I wouldn`t suggest you download any virus source codes until you know what to do with them, in fact to strictly answer your question: No you don`t need to know all about viruses to be safe from them, just the same as you don`t need to know all about cars to drive one. If however you are interested in learning about viruses then check out the sites listed by nihil, that would be a good start.