I took my 560SEL in to get the top tank replaced but upon inspection the core was in need of replacement so they fitted a new radiator. Normally I would do this myself as it's not a hard job. No special tools are needed, the shop that performed this work took a total of 2 hours to remove, replace, refill and test etc. My top tank started leaking around the little return hose at the top of the radiator. This hose runs back to the tank with the radiator cap on it. I removed the hose from the radiator end and the plastic stem that it slides over had disintergrated. I had about 6mm left so I put the hose back on as far down as I could and that stopped the leak in the short term until I could get it fixed. Here is a link to a write up in the DIY section here.