How to change the toilet seat on a Kohler high efficiency toilet?

We just remodeled our master bath and installed a Kohler high efficiency toilet with dual flush (sorry I don't know the exact model). I can't figure out how to change the toilet seat though, the builder installed it for us and I don't know how he did it. The screws appear to go into the toilet, but there isn't a way for me to access underneath the bowl to attach the other end of the nut. The toilet looks all sleek and modern, but it feels a little out of my league to do what appears a normal task.. I fear that if I just back the screws out of the existing seat that whatever is holding the seat in place will fall into the innards of the toilet and we'll have to remove the toilet to change the seat. Help!