I wonder why you would want to swap the engine from a perfectly good car - the whole car is designed to work together and taking out an engine and replacing it with a (brand X- you choose) could cause you more headaches than you want. If you are doing this as a hot rod thing than fill your boots but a well sorted pagoda should serve you well. Unless you have had one of these you may not understand how well they are built and I was one of those who grew up with british cars, but those guys and gals in Mercedes Land did an amazing job with these cars. This is not a simple plug and play like a GM-350 in a Jaguar sedan sort of swap.
I have found my time spent on fixing my car is due to switches that don't switch, perished rubber components like motor mounts and bushings and brake lines, fuel issues / rust .....but none of my issues so far have been "engine" related (touch wood). Just for the record I have enjoyed 100% success on fixing items or replacing maintenance items.
I put about the same mileage on an annual basis on my Mercedes that I do on my 2005 Dodge Ram and I spend more time diagnosing and fixing my Dodge Ram (camshaft sensors, egr valves, etc).
