Bike seat recovering and lowering

I have a severe case of farkle-itis. It is matched also by an equally bad case of the poverty. The co-occurance of these two is common referred to as 'wesley's disease'.

Anyways, my drz is too tall for me. I know you can have your seat recovered and reshaped to be more comfortable on tar and have a gripper cover and at the same time shave two or three centimeres off the foam. So it's an all round winning mod. Is there someone in Cape Town that can do this? How much? Can I do it myself? How?