I wouldn't save only some files. I have saved the GTA3.img 2 times. One time with all the mods. Omfg, it is really full of mods. and then the normal GTA3.img. I've found a forum, where the guys told me to rename the normal ones and then insert new ones. But this was wrong, because you'll loose your files at once.
backup is the best thing you can do.
And yeah, the options work fine, for me too.