Permissible and impermissible items of trade

Q: I have one question - is it permissible to buy cleaned Sea Shells from an Arts and Craft Shop and use it for internal house decoration, eg in the bathroom. 

Q:

1. If women have gold, silver, and diamond crucifixes, aum, and Buddha jewellery before excepting Islam, what should they do with them? Should they have them melted and redesigned or should they bury them?
2. What is the punishment for Muslims selling jewellery for kuffaar religions?
3. Can Muslims wear jewellery that has the name of Allah and ayaat from the Quran in lockets when we don't have wudhu?