The engine in this vehicle is more or less a computer-controlled (either Bosch or Lucas/GEMS, though this will probably be Bosch) version of what Rover was producing from 1960 onward. The engine was actually a "revamped" Buick 215 V8, produced as early as 1953...
It will be best to checkout some of the Land-Rover's Owner Forums for more information, but if you've got cooling system issues, it will be prudent to ensure the famous cylinder-liner issue isn't at play, or worse yet, the other issue related to the engine block behind the liners corroding away.
From what I've learned about this engine, the later Bosch fuel injection system runs hotter than the original GEMS style, which exasperated the slipped-liners issue. Provided the block is still good, a common modification to resolve this issue is to use "top-hatted" cylinder liners that cannot slip.
The Land-Rover Discovery 2 was, and still is, a very versatile and highly capable 4WD / Large SUV style of vehicle. As ANY car will have their own personalities and niggles, if you can get this car at the right price considering its mechanical trouble, I'd say it *might* be worthwhile.
Really, its a shame the USA was never treated to the Rover TD5 or even the older TDi turbo-diesel engine. Powerful, economical, VERY emissions-friendly and far more reliable than the alternative V8, particularly in its latter years.
The V8, like many petrol equivalents from the USA and otherwise, simply converted Petrol into smoothness, "burble," emissions and a hefty cost at the fuel station. It wasn't really all that powerful and not all economical.