I just did the same on my 190E since I was shipping the head off for a rebuild, but I did it before I knew I would be shipping it
It is a 4 cylinder engine, and I found an amazing spring compressor for $12 at princess auto, it works like a charm, never slipped, always fit right in and made spring work a breeze.
I was able to pull the seals off with some pliers, I'm not sure if they are the same on my car, but I was very surprised they came off so nicely compared to other heads I worked on, but prying them up with a flat screwdriver also helps, just make sure not to scratch anything
Very good DIY job, I also had the cylinder head off, so I did not need pressure to keep the valve in place, but fabricating a fitting from a spark plug, that's pure genius, I would have never thought of it
Great work Don keep it up
xp