my wife had a zoop. when the battery died, you need to change the o-ring along with the battery according to the instructions. unfortunately, the dive shop did not have the o-ring, and ended up buying a mares computer on the spot. i would suggest you get a couple extra batteries and o-rings for it.
You bought a new computer because the shop didn't have an o-ring? They refused to re-use the o-ring? The Suunto SKU for a battery replacement includes the o-ring. Sounds like your shop did you dirty.