I personally think we should stop explaining this stuff. People should use a little common sense when dealing with this stuff.
"Oh my god! I want to use a trunks replacement model, but I don't know how do it!"
"Well, open up your ESF folder in your Half-Life directory . . ."
"Really? Wow! What else?"
"Well, see that folder named models? Open that one"
"Wow! Really? I wouldn't have thought it would involve opening that folder!"
"Now, open the folder that says: 'Player'"
"oh, really? Now what?"
"Now see the folder that says: 'Trunks?' Place the model that's named trunks.mdl in there, overwriting the other one in there. Then take the ssjtrunks.mdl and place it in the ssjtrunks folder. Hey, did you ever notice how .mdl is spelled similarly to the word 'model?'"
"Wow! Really?"
Common sense people! Not to mention there are a million sticky notes posted at the top of this forum.