Hosting for Absolute Beginners

[tinkthank]

Would anyone be kind enough to either post here or post a link to some information on what an
Absolute Beginner (such as: myself) needs to know to "host" MP games on a Windows computer? I found the information posted here by very helpful people to be fascinating, but not explicit enough for the Absolutely Computer Illiterate (such as yours truly).

Some of the Things I Would Like to Know:
- The Obvious (Is Not Obvious To Me): How do I figure out my IP address? (I dont need that if it is PBEM, right?) Someone told me this changes from day to day, how do I find it out? How do I figure out which "Port" to use?
- Safety: Someone told me that if others find out my IP address and port information, they can "hack" my computer, that I should never let others know this. Is this true? So when hosting a DII game, I am making an exception for nice DomII players who will never hack me because they are per definitionem cute and cuddly and friendly etc., or is there some trick I must know? Does somehow a "router" come into play here, and can that cause problems?

Thanks very much.