problems with mercedes sprinter van

I bought a new mercedes sprinter van in nov 07, and since day one have had problems with diesel leaking into the oil, and have had it back to garage on numerous occasions to get oil changes, all he whle being told that they were seeking solution in Germany, the solution after three years was , to drive it on long journeys more.
A few weeks ago, major bang and the engine is knackered, they now tell me I am out of warranty and have to pay for repairs myself,has anyone got any advise on what to do , is it a legal issue