As I said previously, with proper tool it is less than 1 hour.
How far away from the Glasgow brothers are you (forget thir name) ?
They deal in the older mercs and will probably have the tool, as they are the register captains for the 190 models (same suspension) in the authorised club.
Your total cost with them would be of the order of £100 inclusive, in my opinion, and they would not have to dismantle the suspension so nil alignment issues afterwards.