With the risk of stating the obvious, they are very basic so you should have no problem in seeing what may be wrong. You will be able to buy just about any part needed from the likes of Paddocks, etc, and most of it just bolts or screws on. Parts are relatively cheap compared to modern cars and classics the likes of MG's, Triumph's, etc.
If it has been standing a while you will probably need to do a bit of work on the brakes (no servo, drums all around). New points and plugs would probably help but as stated above, fuel consumption is poor anyway. Swivel balls may be rusty and/or leaking but you have probably had dealings with them on other Land Rovers. I had a leaking fuel tank when I restored mine so just bought a new one (about