Most of the construction is nuts and bolts and spring clips, the same as any other Land Rover. For the most part, they're not mechanically difficult. What's needed more than engineering expertise is the patience to free off rusted or seized components. As the TD5 is controlled by a "computer" (well, a printed circuit board in a case) you may need specialist equipment (or take it to a garage that does) to identify faults and get access to various data that helps you assess the condition of the engine. I have a Nanocom for mine, which was one of the best tools I've bought for it. Of the various Landyzone denizens there are a few who entrust maintenance of their TD5s mostly to a garage and manage to survive, like 110 Woman. And she manages to do it on a nurse's wages too! So it's not impossible.