I agree with the suggestions so far.
Just to add another,
Pull that rock, rinse it really well, and then keep it in a rubbermaid tub of saltwater with a powerhead and a heater until it's cured. Meanwhile let the display just hang out with the shirmp and sand. This way the shrimp have a much better chance of survival and you may not lose anything.
And another...
Also, whatever you decide to do, some carbon filtration in that water will help to remove some of the stinkies (pollutants/die off) that are already in there now. That would help a lot if the rock is removed for cleaning and seperate cycling, but if the rock is still in there it will continue to pollute the water for at least a little while.
Marc's rock rules, but dead rock still needs cleaning/cycling dead stuff time.