[MBZ] dial gauge question

[tom savage]

I need to replace a rear wheel bearing on my 300D.  Everyone keeps 
saying that a dial gauge is needed to properly tension them, but Sears 
and AutoZone claim never to have heard of such an animal and I'm not 
entirely sure what I need.  Is this close?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7578341295
Thanks,
Tom