Re: Adding shower to half bath.
It will be a relatively minor difference because the supply lines are already there or nearby. If you're on a slab, then hooking up the drainage will be costly because the floor will have to be jack hammered out. If you're on a raised foundation there shouldn't be too much trouble to tie into the existing lines.
I would severely caution against installing a shower that is less than 32" square, larger is better. The reason being is that anything less is going to be so claustrophobic that you won't want to use it or it will be difficult to use.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!