Belethor's shop was closed for days and days. I waited outside his shop for an our in increments. Still would not open. I went into the Hall of the Dead in whiterun to find his coffin. Ok so Belethor is dead and I need him alive to buy some stuff from him in whiterun. I like to keep all my merchants around. I'm not sure how he died. Is there a way to resurrect him even though he is still in a coffin or would I have to spawn a new Belethor?
I've read on other forums that creating a new belethor brings him back but he has no merchant speech. So he's around but he's not selling anything. What do I need to do to get the old Belethor back?

If you are on PC you should be able to bring him back through console commands.
On consoles however, i believe he will remain dead unless you resurrect him a a zombie.

Also what all this about bodies turning up at the hall of the dead in coffins, i have never seen or heard anything about this before