Huh... maybe not in your case on the milage. Sounds about average for a vehicle that year. There's a good chance the previous owner neglected to keep up with it. Hopefully they at least did oil changes and tune-ups reasonably often.

 

Appears a common issue with the Disco. Evaluate to engine condition and consider head gasket, front cover, and water pump while your there. You,ll be replacing the exhaust manifold gaskets, and valley gasket as well. Throttle body gasket too. With this much work it is definitely worthwhile to replace plug wires and plugs unless that was done recently. With the heads off, its an opportunity to service the heads.