No problem saving the seeds - cut the pumpkin in half, and scoop out the seeds. Wash the seed in a colander, rubbing it between your hands to get rid of the fibres, and then shake off as much water as possible.
Spread the seed out on a plate to dry. It needs to dry as quickly as possible, but without getting too hot, for example on a sunny windowsill or near a radiator. Seeds can be stored in a cool and dark place and will keep for 6 years.