A good exhaust shop will be able to handle the converter for you with no problem.
The price of 1,100 --1,900 hundred seems a bit high. Is this from the dealer (MB)? There are several after market american made lifetime warranty converter assemblys for 600 to 700 dollar range.
They will perform very satisfactory to your liking. How do you know for sure that is the problem? What is it doing? How many miles on the current converter?
Also a good exhaust specialist will be able to check the converter and tell you how restrictive it is. Flow going into and exiting the converter.
If you do choose a used converter make sure its not damaged, ie cracked inside noisey inside when you shake it etc. Again a good shop will be able to install one with no leaks. And guarantee it (work only) naturally not the used converter. Good luck.
1989 420SEL 105575 miles
1990 Chevrolet E-Cab C-1500
1989 Olds Toranado Trofeo'