I need to top up my coolant in my 2012 E350 coupe but the process seems pretty confusing and I don't want to mess it up. My manual says to use either MB 325.0 or 326.0. but I don't know whats in my car right now as I recently bought it. It is yellow if that helps. Should I completeley drain the coolant I have and replace it with one of the two recomended coolants or am I able to add one to what I already have. Advice would be greatly appreciated.
Thanks!

If you just acquired the car and it is +10 years old better drain the coolant and replace the fluid. Same thing with all the "long last or forever" fluids like steering and differential fluids.

or just top it off with either.

Or take to dealer and ask them too.