Whats the wrong with my car if it has acceleration problems and the check engine light comes on?

I couldn't find where to put a description, so here it is:

For the past 7-8 months or so, I've been having problems with my 2002 Hyundai Accent. When I bought it used it ran great for about 3 months or so, and now I'm not sure why it doesn't.

Here's what it's doing: It doesn't accelerate quickly, and lacks "power" behind it. If I try to accelerate too fast, it will jump back at me and my "check engine" light will go on. I've noticed that it's also more likely to do this if I've been already driving a while, or if it's a really hot day out (she drives better at night). Sometimes the front end also gets louder than normal. It lacks any power whatsoever when I try to go up a hill and I can't push it for fear of it dying. Also when accelerating, the RPM gauge will shoot up really high for a minute and then come back down. Sometimes it seems the RPM needle isn't where it should be. The RPM needle also never fully rests on zero.

I had one mechanic tell me that the reading on his diagnostic machine said something about the transmission, not the engine, and to get a flush to be on the safe side. Because the needle on the RPM gauge never rests at zero, I had a different mechanic tell me it was the sensors around the transmission and he also recommended a transmission flush because the fluids were black. He opened up the vehicle and within minutes of doing a flush, he said it was a broken bearing. He said to fix the broken bearing I'd have to get my transmission rebuilt. He felt that the broken bearing rattling around is what's throwing off my sensors. Ofcourse, I don't know what to believe because I'm not a mechanic, and I feel easily swindled.

My questions are: 1) What do you think is wrong with my car? What do you recommend? 2) Will a rebuilt transmission fix all of the above problems? 3) If I get my transmission rebuilt, will it also fix the sensors, if that is indeed a problem also? 4) Does it take longer than a few minutes to notice a broken bearing? 5) Is there any truth to the broken bearing affecting acceleration and the RPM gauge? 6) Why does my "check engine" light come on if it's a transmission problem? Is the transmission issue effecting my engine at all?

Feel free to answer any of these questions, it'd be a great help. :) Thank you!!!

One thing you should know is that if you haven't flushed transmission or for a long time then don't get it flushed. All that build up acts as a lubricant. I was just having car talk with my friend and he told me this from his brother who Owns a transmission shop. He said his family has never flushed their transmission and they own 5 cars. There are Sly mechanics out there just like there are shady auto dealerships. You have to be careful. I hope I helped! And I encourage more people to try answering auto questions online so research on auto problems will be more productive. Just trying to part of a good cause , Good Luck I hope I gave feed back quick enough :) and BTW, mechanics will ask you when the last time you've have transmission flushed, so a customer will get it flushed and then wonder why weeks- 2 mos later why there transmission went out.

To addres the original question, have the codes read and search for possible causes for the code to see if the mechanics are correct.