I just saw your post. Here's how to take any model and get it to replace Kyle. First, I would recommend you download a copy of PakScape, a very easy-to-use program to handle .pk3 files. You can download it here.
Open models/players/name of model. Rename the name of that model to kyle. Delate the old name of the model and put the kyle one under models/players. Next, edit the model_default.skin file. Rename everything in there where you see model/players/name of model to models/players/kyle; however, do not rename the ones that have info about the caps-those are for the cauterized parts you see when you cut a limb off of a model.
To use sounds to replace kyles, rename the sounds/chars/misc/whatever the model's sounds are to sounds/chars/misc/kyle.
And that's it! Name and save your .pk3, and then either slip your new model in the GameData/base folder, or make a folder named what you named your .pk3 and put it in the GameData folder, and then when you load up the game, go to Setup, select mods, find you mod, and click load mod. Voila! Your model will replace Kyle with whatever map you are playing!
Good luck. If you need any more assistance, let me know.