Belt tensioner

I took my car to a local guy just to have him tighten down my squeaky belt. He told me the belt tensioning pulley system on my car no longer works because the small shock was dead. He said the dealer could do it for me, so I called them. They told me that when the shock dies, it usually breaks the tensioning unit at the same time, and I would also need to have that replaced in addition to the small shock. I see that the rod with the long bolt on top that goes down into the tensioner is unhooked from whatever it connects to inside. It doesn't look like it snapped or anything though. It just looks disconnected. I am wondering if whether the dealer is making me buy something I don't even need (i.e. new belt tensioner) by saying the tensioner breaks when the shock dies, or if it is possible to just insert the tensioning rod back into place and save the couple hundred dollars it costs for the new tensioner?