Chrysler Repair: intrepid 96 wont start, car wont start, ground cable

Question
i bought an intrepid which i thought was a good deal but now im stuck with it, i got the engine rectified and reassembled now the car wont start i had several parts replaced the check engine lite doesn't turn on the mechanic told me it might be the computer or just a ground cable and needs to find the diagram which he doesn't have it also has the alarm armed and have no control to deactivate it i just read a few answers and think that the alarm i will be able to deactivate it but what about the check engine lite what you think the problem might be the car doesn't even crank all parts that were bad were changed except for the gas pump which the mechanic told me no to replace it until he gets the other stuff working to see if the pump works please help me

Answer
way to many issues to deal with at once..
No start first then deal with others. Battery good? Red light on the dash to say alarm is active? try turning the key in the door locks driver and passenger to see if it will disarm? How am i suptose to know what the check engein light is on for unless u tell me what the codes are???  there are only 600 or so different ones.