Here is the spec on your old one
http://processorfinder.intel.com/Details.aspx?sSpec=SL6PDHere is the spec on the ebay model.
http://processorfinder.intel.com/Details.aspx?sSpec=SL6S2#Not much difference other than the Core stepping on the ebay model is an older C1 stepping as opposed to the D1 stepping on yours. The tray processor designation difference only means it was sold to an OEM(Dell)
Newer steppings typically have some type of improvement over previous steppings of the processor. It should work but if you really want to be sure,here are some SL6PD models on ebay
http://search.ebay.com/SL6PD_W0QQfrppZ50QQfsopZ1QQmaxrecordsreturnedZ300