Remove top radiator hose from thermostat housing.
Loosen 2 clamps on the little hose.
Remove lower radiator from thermostat housing.
Remove the 2 bolts that hold that housing to the head.
(Get a new gasket)
Replace the hose.
Install in reverse order.
Have some emory cloth or sand paper to clean up the oxidation on the hose connections.
Not hard to do.

Edit: put Never Seeze(sp) on the bolts when installing.

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1985 300D California w/cat. (257,000 + Miles)
1980 300SD (208,000 + Miles)