I've done a little research in the past hour. The engine the C43 AMG uses is called the M113. it comes in 4.3 5.0 and 5.5 liter versions. They all use the same mounts (ie: c43 mounts are the same as e55 mounts) and are packaged more or less the same. The 4.3 and 5.0 engines are very common and not at all expensive. The 5.5 AMG motors can be found for a good price as well. There are actually two E55 motors on ebay right now for less than 3 grand and are complete. if you can get a full motor and transmission the swap would mostly be there. Note that stock brakes and suspension would hate you. So either amg suspension or aftermarket stuff (koni, bilstein etc). A lot of lines would need to be redone as well like the fuel line once it gets in the engine bay. You will also need a new exhaust fabbed. If we assume $3k for full motor and transmission then I would say 5 grand getting it in the car assuming the suspension stuff was already done. Of course if you can score a cheap front clip then your life would be so easy.