OK, let me see if I can answer what I think you are asking:
You will need to use firewire (IEEE 1394) to capture the footage from the camcorder to your computer for editing. If you have two camcorders, then you will obviously need to repeat it again.
You will also need a video editing program and a computer capable of editing the footage that you captured. When you edit HD footage, you will need a more powerful computer than you would need for SD footage.
Once you are done editing your footage, you need to figure out what you are going to do with it. Will you post the footage on the web? Will you make SD-DVD's with it? Will you make Blu-Ray discs with it? If so, you may need to purchase additional software or hardware for your needs.
You mention the switcher, but I don't see how that will come into play, and do not think it is needed.