Used '97 Discovery need some direction

[RhorseDisco]

Relatively new to the Land Rover world. I've had my '97 Disco SD7 for about 4-5 months now and I had bought it used. I knew it would need work from the start, but now I'm not sure where to begin. Recently replaced brake light switch. The list of problems are as follows: High idle and also sounds like an old tractor when running, Engine dies when at a stop light/sign, left tail light and license plate light are out even after replacing bulbs, Leaks of engine oil, transmission, and brake fluids, frequent overheating after being driven causing coolant to boil out. Attempts at solving problems have been getting an oil change and of course just ensuring all caps were firmly closed. Any suggestions on where I should start or sources of the problems? Any help would be appreciated. It's my first ride and I'm no mechanic, but I'm pretty quick to learn. Thanks.