Does anyone know if I need a special tool to change the fuel filter or what size wrenches? Also, how long should a filter last? I have 165,000 miles but am unsure of the last change or if there was one.

Secondly, I have fan problems that seem common. My first fan stopped working so I replaced it with another used one I bought on E-Bay..I know I know...but it was only 20 dollars so I thought it might be worth a shot. It worked for two days and stopped. It just free spins and doesnt lock up when it is supposed to.
Also, niether of the auxilarary fans come on when they should. I replaced the sensor (new from Mercedes) and inspected all the wires and resistor.
The fans do engage when the AC is used, so I know the fans themselves work. Im lost on this one.

Please help! Im at wits end with the fan issue. Its around 100 degrees lately and the only way for it to stay moderately cool is to be in motion.

Thanks guys!