They are mainly asking for help as the Japanese specialists are having to monitor all the reactors at once at the plant, with damaged infrastructure, no sleep for days, and no idea if family members are dead or alive, so they need to be relieved to rest. It also doesn't hurt getting 3rd party opinions.
At the moment the cores are still under control, and as long as they keep the sea water in for a couple of weeks, they'll be too cold to suffer a meltdown.
The building are built to explode the way they have done. All leaked radiation, for what little has been released was all locally based, and soon drops to normal levels as they are not alpha particles from the core which are the ones Chernobyl pumped out.
