yeah, THL is going to need a vertex shader to the cell shadeing back, but as far as I know the non-htl mode should still work, there are a few things to remember one of wich when you make a cell shaded model you are going to want to make sure that is i heavely smooth shaded, otherwise you're going to the a weird not-cartoony looking effect on all of your models.
the texturs should be extreemly simple, you probly shouldn't use more than 10 colors, make it look like someone who's naever used a computer in there lives did it in MSpaint, one of the nice things about cell shadeing is that makeing new textures is generaly super easy