Frankly, you just need to dig into it. You will need to drive out the old pin in order to replace it. Inspect also the bearings at each end of the auger shaft and the support bearing at the back of the impeller for slop. Have an assistant start the machine and engage the auger. After it has run enough to blow out the snow and ice, have a look at how true things are running looking for problem areas. Shut the machine off before inspecting too close!

I got the pin out and the rod is definitely snapped. Only problem is Sears shows a back order until 3/31. Is there another bar that would be an equivalent replacement - model # is 247.88790 - 28" model.

http://forums2.gardenweb.com/forums/load/tools/msg021703417584.html

See that link. You'll probably end up doing a similar job.

Did you search Amazon.com for the part? I've bought some parts for my Craftsman (built by Murray) on Amazon.