The real questions are. Why did you charge the battery? Does the car crank and not run or not crank?

Changing the battery in this car is a non issue and no there isn't something to block others from changing a battery. The 9V memory saver plug in during a change is just to prevent loss of radio/ clock and other settings.

I have a 97 E320 parts car that has survived sitting for 5 years without being run. With unsticking of the starter and fuel pump, it has survived dozens of battery changes over the past year without any memory saver. Install battery, turn key, motor runs.

I've does this to my sitting for 2 years 97 C280 with no ill effects ad well.