Just won't accelerate

So I have a 2003 Saturn L200. My car started off great when I first bought it, it just didn't shift gears the best, but it still shifted. Then, after a week or so of having the car, it messed up. Here's the destruction of what happens: first off my speedometer won't move at all(it stays at 0mph no matter whether I'm moving, parked, etc.). Also, the vehicle doesn't shift gears at all. I'll press down the gas peddle and it'll move but it just won't accelerate. And my RPM gage is off the wall going to the high 3's. And I know that's not good so I have tried to not drive it at all. Then I was told to replace my speed sensor, which I did. The car worked fine for about 2 weeks. Then the problems started all over again. I've replaced the speed sensor about 3 times (all brand new). But the problem just keeps occurring. Now it's getting to where it messes up every other day. So I checked my oil and filled it up, and the next day it was bone dry. So I filled it up again and still my car was messed up. Then I was told to take the speed sensor off and clean it. I did that, and there was a black liquid in it so I wiped it off and put it back on and it still didn't work. I believe it may be leaking oil onto my speed sensor but I'm no car specialist. Somebody please help me and tell me what to do about my car. I can't afford a new one.