I could picture using a little 1/4 " socket and a small C-clamp to press the plate on, working from side-to-side. I was going to try the hammer and dolly method, but I was worried that I might bend the pins so that they weren't square with the back plate.
I would probably go for it now, or maybe buy the tool. At the time I needed the chain done on the 300E we hadn't had the car that long. It was our first Mercedes and I was still a bit apprehensive to dig into it. That feeling went away a long time ago. Anyway, I let the dealer do it. The labor was $275 (a few years ago).
Experience is something you don't get until just after you need it.