That sucks. I know nothing about Pentax gear, but if it's anything like Nikon and Canon, the 50mm lens should be pretty inexpensive. I would bet the repair would cost more than what you could replace the lens for.
"I thought that because fewer wolves meant more deer, that no wolves would mean hunters' paradise. But after seeing the green fire die, I sensed that neither the wolf nor the mountain agreed with such a view."
Aldo Leopold