1998 Chevy Cavalier ETS Light, Check Engine Light, Shaking

My girlfriend has a 98 chevy cavalier z24 with about 90000 miles. One day she was coming home from work, while on the highway, the ETS and Check engine light came on so she started to get off on the first available exit. While driving to the closest gas station the engine started to knock/stall and she said she thought she saw some smoke when she looked in her rear view mirror (but it was dark and she couldn't tell if it was exhaust or from engine, smoke stopped when she pulled over)

took the car to pepboys (realizing this was a mistake) they charged her 500 bucks for new coils and plugs and an oil change, reset the lights, it was fine for a day. Then the check engine light came on, I popped the hood, and noticed that pepboys never put the oil dipstick back, I looked around and found the dipstick stuck against the radiator fan, I cleaned it off and put it back, I also replaced the gas cap hoping that was the cause for the check engine, but it didn't help

she brought it back to pepboys, explained the problem, the apologized about the dipstick and offered free diagnostic for the check engine. Said that there was no problem and light needed to be reset, they reset it, 2 days later, check engine came back on, she threw some fuel injector cleaner in the gas tank, hoping that would help, 3 days later, old problem came back (ETS, Check Engine, and stalling, car turning off, steering locking up). It was almost impossible to get the car to drive a block back to pepboys.

the people at pepboys don't seem to know what they are doing, and I don't know any good mechanics in the Burbank area, any ideas why this is happening?

i read other peoples problems and some suggestions were, abs sensor/wheel speed sensor, throttle position sensor, lockup torque converter. But most of those problems had to do with the ETS light, but car still functioned, or stalling only while making turns.

any help would be greatly appreciated, we are just some poor kids that can't afford to make unnecessary repairs, so hopefully your experience and knowledge can help us get right to the root of the problem.