here is the install guide for installing the b&m shortshifter: ecelica.com: b&m shortshifter install
although this is b&m, any shortshifter install will basically be the same for the celica
credit isaac for the guide.
and the benefit of the shortshifter (as already stated above) is very straightforward: shorter shifter = less movement needed to shift = quicker shifts. and quicker shifts obviously = slightly better times