Ok, so I bought a hood ornament from Ebay for my car...

First year for the 124 chassis in the US was 1986. It was available in Europe a year earlier.
As others have said, yes, you go the right ornament. And they're also correct that it will be an awful job to get it in installable condition. The whole mess is spring-loaded to grab the grill shell and once taken apart, well, yuck. BTDT, had the sore fingers to prove it. Wear eye protection.
I'll post a pic of what a brand new hood ornament looks like so you have an idea of where you're headed.

A new ornament comes as one piece. An installed ornament can be removed intace *if* you know what you're doing. (You reverse the installation.) It's not intuitive unless you've installed a new ornament. The seller obviously had no clue what to do so he probably forced it apart to remove it. It may or may not be repairable. Like i said, I'll post a pic of what a new, never-installed ornament looks like. You drop it into the grill shell hole, open the hood, and then grab and twist the black u-shaped piece a bit to release it and it snaps down (up) agains the underside of the grill shell.

Here's the pic:

http://www.bos-engel.com/benz/ornguts.jpg