Land Rover Repair: ac fan/Tachometer/tapping, import repair, rocker shafts

Question
I have a few questions about my 98 Disco with 123k. First,I took it to an import repair shop for an overheating issue. No leaks, but the left ac fan in front of the radiator stops after about a minute on. The shop checked the cooling system and removed the radiator and cleared an apparent 40 percent blockage. I got the truck back nice and cool but the AC fans no longer running. How important are these fans for the coming summer months? Second, I got an oil change today and realized later that the tachometer is not working-could this be a reult of the work that was done on it/could they have not a wire off when working on it??  Third, When I acquired this LR from a relative, it had a tapping/knocking sound from the upper level of the engine. I was told that it could be the "lifters". What are lifters? and Is this truck worth keeping? Thank you.  

Answer
The electric fans are needed to prevent overheating in hot weather.

I don't think there is any wire they'd hit while changing oil to kill the tach but anything's possible, I suppose.  Look carefully.

Lifters are the pieces between the camshaft and the pushrods.  They are part of the system that opens and closes your valves.  Lifters are seldom a source of noise in Rovers.  Rocker shafts go bad, and people also confuse spitting from the exhaust manifolds with internal engine noises.  Check those things