VCC is just power source, I don't know what for, but you will really need only 3 wires. If you don't believe me, read http://wiki.openwrt.org/doc/hardware/po … .listening
All you have to do to connect the router via serial cable can be seen in the video, there's not much more I can tell or describe you. You will use putty, but you will have to set it to use serial port and write port name - which one it is you will find in device manager after connecting the cable (if you are using windows), so no telnet to ip yet, have you watched the video at all? Debricking section and how to upload firmware via tftp is in the other link, just read it *carefully*, don't worry if it's for different router, most of the procedures are common, you will only have to use different firmware image, exactly the one for your router and revision.
Don't worry the theory, it's normal to be afraid of new things, but at least please read those wiki articles, there's no much sense in writing it down here with my own words, there are mostly written with far better English than I could tell you When you will have the cable ready, soldered and router communicating, you will be more clever, you'll see. When you exactly ask, what part you do not understand, there are many good people in here trying to help, but if you will not read yourself what was given to you, no one can help help you.
Openwrt is fun at the first place and fun costs money, worst what can happen is, that you will lose $17 worth your device. Many people in country where I live are working the whole day to earn that, but if you will learn, you will manage that - with a bit of skill and good luck