98 Pontiac Grand Am se help!!

Okay, I took it to a man who owns his shop next to his
house . This is what he fixed. He said there was a engine misfire
code 0451. Multiple cylinder misfire. He replaced the coil cover,
boot set, 1 spark plug #4 cylinder. Okay i tested out the car it runs
better. But still doing that hesitation again. Also, I was at the
grocery, I had the car at drive all of a sudden the car wanted to
stop .So i put the car on the neutrol and all of a sudden the rpm
started to go up about the number 6. So i decided to turn off the
car. Then restarted it and it turned back on. but still giving me the
hesitation . I ve noticed also when i start the car i have to give it
2 cranks then it will start after pressing the gas pedal 2 times.
Does this have something to do with the problem with the hesitstion
also? I went back to the mechanic and told him about the problem. He
said he coudnt find anything wrong with it. He said to leave him the
car for a couple of days to see if it hesitates on him. Did he cheat
me out? Also, Please help me find this solution on my car ?