Need help with my 98 Acura CL 3.0L

I have a 1998 Acura CL 3.0l automatic with about 254991 miles on it, for some reason it's been using a lot of gas and I don't know why. How do I fix the problem? Also I had a mechanic replace the engine temperature sensor and he broke it somehow after a few days my car started to over hear so how do I get the sensor out of the housing? Also the mechanic said my oil pressure switch was leaking all my oil so I paid to have that replaced as well but my car is still leaking oil, when I'm driving down the road an I'm pressing on the gas my car makes like a whistling sound and only when I'm pressing on the gas but I don't know why or where it's coming from it's been happening for a couple months now, and when I turn my blinker on the lights on the odometer board blink with the blinker as it's blinking, the light get dimmer too even the head lights do this when I turn on the blinker almost like it's loosing power or something? What do I need to do to fix my car? Please help me out.