LiteIcon is a pretty self explanatory program. And it's free.
Whilst the OP said they didn't want CandyBar, I still recommend it.Very good program.
I used interfacelift icons, downloaded, found the icons I wanted to change,c icon from interfacelft, get info on the standard icon, select the top image on get info and
v. It was tricky at first but then I got the hang of it, but if you want to do all icons, like new folders and stuff, I would recommend Candybar also. They give you 25 changes free, then you have to purchase it.