Skype works with a very wide range of microphones and webcams. As long as you have the drivers for the webcam, then you should be able to select it in Skype.
Get into Skype, look at the top and look for Tools. Click and go to Options. In the options on the left side, go to the Video Settings. It should automatically detect a webcam if you have one plugged in. Make sure you have the webcam set up how you would like.
As for the microphone, it's plug and play as well in terms of how it works. But I wouldn't try using an old microphone though. The sound sampling quality is usually a bit lower than a more modern mic or headset. I would go out and buy a cheap 10 or 15 dollar mic or headset and use that.
After you get your mic plugged in, go into Tools, Options, and Audio Settings. Choose the appropriate settings and you should be good to go. (Also make sure you don't forget to unmute the microphone. Sometimes Windows Sound mutes the mic because it doesn't detect it so you need to unmute it. And make sure there isn't a manual mute button on the mic that's switched on or you won't get sound regardless.)
After that, you should be able to make video calls. Make sure you have decent lighting in your room or else the webcam image might appear to be a bit too dark to see yourself/the other person properly.
Naturally, if you have any more specific questions, then don't hesitate to ask. I use skype on a moderate basis and I'm fairly familiar with it.
Edit: This is the headset I use. It gives me good quality sound.
http://www.mrgadget.com.au/catalog/images/logitech_clearchat_style_pc_headset.gif. The webcam I use is actually a 3 megapixel camera that offers a webcam option. This is my camera:
http://images.tigerdirect.com/skuimages/large/DXGusa-305v-mainx.jpg