Land Rover Freelander 1 Engine - L Series, TD4, KV6, K 1.8
There were a number of different engines fitted to the Freelander 1 during production be sure to identify yours before asking for parts.
2.0 Litre Diesel (L series)
2.0 Litre Turbo Diesel TD4
1.8 Litre Petrol K Series
2.5 Litre V6 KV6
There were a few age related changes to the engines and so the date of the engine is also helpful.
In terms of inherent weakness the diesels appear to be the most robust although the TD4 has a cast crankshaft which has been known to fail (by fracturing).
The K series petrol has a poor reputation but my experience it that it has bad press! Yes, head gaskets can fail, mostly, not always, as a result of overheating and / or low coolant levels being ignored. There are improvements that can be done to improve reliability when rebuilding. Multi-layer head gaskets, strengthened oil rail (which the head bolts to), upgraded head bolts etc. If you are conducting a rebuild it is best to read up on the modifications and consider your use for the vehicle and then decide which seem appropriate and cost effective.
The KV6 is a lovely engine and being a V6 is very smooth and punchy. Again, it can suffer from coolant leaks which if ignored can cause further damage. It is also a large engine in a small engine bay and so is harder to work on.
The diesel engines have timing chains and so these last longer than a timing belt. The petrol variants have timing belts and these require routine maintenance to prevent breakage with resulting catastrophic failure of the engine (due to valves hitting pistons).