I've flown a few Cessnas with Thielert diesels. Overall it is a very simple beast to operate but there are a few things that are different. If you are just using the aircraft to cruise around and have lunch, you probably won't notice these differences all that much. If you are operating for training purposes, you'll find them. One thing is that the aircraft is less willing to slow down. The prop will continue to keep the RPM high and you will still have a bit of thrust from it, you'll have to decelarate below 60kt to get the RPM down and then all of a sudden your glide path gets steeper. Keep that in mind if you want to use smaller fields. Also your weight carrying capacity will be quite a bit less than on the Avgas fueled version. The other gotcha is that almost every section of the Emergency Procedures ends with 'land as soon as practicable, expect an engine failure' as you will need electricity to keep the engine running.
As for engine controls, you will not be able to set power 'by ear' as the sound will not change. That means paying more attention to the thrust indication on the engine display or learning to set power by remembering lever positions (1cm forward equals this much power for example).
Hope this helps.