I'd go visit a local Toyota dealer with the registration number before buying, and see which factory recalls their service department can find that haven't been done to the vehicle, the injector seals in particular!
Regarding the past service history, it's virtually impossible to answer your doubts without knowing who did the service work. Was it a specialist 4x4 Landcruiser shop, an old boy with years and years of in-depth knowledge, or a corner garage? Bear in mind, often at a factory dealership, the junior mechanics do the basic servicing, and the more experienced guys do the tear downs.
How much work did the past service provider do to the vehicle, just regular servicing and standard consumables for the age/mileage of the vehicle, or much more? And, did they use genuine Toyota parts or not...?