Dodge Repair: cursed 98 dodge avenger, oil pressure gauge, neutral safety switch

Question
hey pete, here i am again. my car was having what seemed to be battery trouble, then started in N but not park, was told neutral safety switch. I took it to a mechanic - he found the battery had a bad cell, replaced it, replaced the alternator belt and air filter. Picked up the car drove 12 miles and the oil pressure dropped and the oil light came on - I called and he said probably trash  from the bottom of the pan stopping it up. He said to try and get it back to him but if the light comes on - do not drive it. When i started the car again - it drove fine for 10 miles and then the same thing (oil pressure dropped), sat there for a minute and then started it and drove the other two miles back to the mechanic. And another $128.00 later, picked up the car, drove it back to my job 25 miles and then when i left for the day the check engine light came on and has stayed on. I haven't driven it for two days. He said that he dropped the pan and cleaned it - the screen was almost stopped completely up and then he changed the oil and filter. The pressure gauge is at half way. I don't know if that is ok, but what would caused the engine light to come on. DOes it need to be reset? My manual says it it ok to drive it with the light on - can it be some kind of sensor? I am worried. One day costs 207.00 and the next 128.00 - not good right here at Christmas. I was told to take it to the auto parts store and they can hook it up to check it? is that right. Any advice. The oil pressure doesn't seem to be as high as when I drove it home from the shop? Never used this mechanic before and don't know if I need to go back to him? Help if you can. When i press the gas down the oil pressure gauge does not move up. Thank in advance for your help.  

Answer
Hello again hun
your mech who you brought your car to proulbly just did a eng flush.
And he would have to change the oil when he did that.
on the eng light it needs to be reset .If try want to do this you can your self take off the neg cable for 5 min hook it back up should rest and stay off.

and  keep a eye on the oil pressiuier gage it should run half way it could be a oil pump on the way out .
Good luck to you again hun and if you need more help u just ask me pete