1. By models you refer to are the KV6 files which are in the kv6 folder. You download things, & unzip them into that folder, replacing the original file. Easy as pie.
2. You use a program called Slab6 to edit them. You will find it here: http://www.advsys.net/ken/download.htm
3. These programs aren't rocket science. I don't know about scales of 1 to 10, but if you're intimidated by computer stuff, modding might not be your bag. Ace of Spades is probably the easiest case-scenario, though, for someone who is interested in game modding. It just takes some patience is all.

http://ace-spades.com/forums/search.php?q=modding

Im new to computer games that let you change the gameplay appearance. So realisticly I have no idea how to do it. I see people are changing the player skins and gun skins and I want to try out a couple ideas of my own. What program(s) do you use to do it? and what is the difficulty level on a scale of 1-10. Im probly at 3, or a -1 to some of you. Any help would be greatly appreciated.