The first generation Magnums are fairly straight forward to replace the chain. If it seemed like your fuel economy was dropping or the engine wasn't getting as warm as it used to, the chain may need replacing. I usually replace them in the 120,000 to 150,000 mile range. While a shade tree mechanic CAN do it, it takes a specialized tool to remove the harmonic balancer.Vans are pretty tight on room but an experienced mechanic should be able to handle it with no problem.