Considering im pretty limited to tools and am not to mechnically inclined as this is my first mustang, how hard are the sending units to change if i did it myself?? What tools would i need and also why dont you think it could be the voltage regulator in the cluster
i've had the same exact symptoms in two cars, both times it was the sending unit. it's pretty common.
they are not hard to swap. there is 3 bolts inside your gas door lid. you remove those 3 bolts (i think its 3, might be 2?) and that will allow you to wiggle the filler neck out later.
there is one retaining bolt that holds the filler tube in place. this bolt is near the end of the tube where it enters the tank. once that is out, theres a metal bracket that slides free. then there is just 2 straps that hold the tank up. you remove those bolts, and i lay under the gas tank. the LESS fuel you have, the better here.
i let it down onto my chest, and manuver it off me while sliding out from under it. from the rear of the car, there are 2 lock rings on the top of the tank. you just need a flathead screwdriver and a mallet. tap the retaining ring free, lift out the sender, drop in the new one and replace with new retaining ring. the senders always come with a new one.
the right side (from back of car) is the fuel pump assembly, the left side is the sending unit. so in total, you need up to these tools;
jack/jackstands, 3/8" ratchet/sockets, flathead screw driver, mallet.
the last time i did mine, it took me 20-30 minutes. it get's painful if you have alot of gas in the tank though.