Q: Error code for engine wiring

We bought it for over a year now and it looks really great. Car has a stalling problem. There's an erro code but we forgot what it is, the engine light is on. the mechanic who checked the error code forgot the code too. But he said it's an engine wiring problem or fuel injector. We've been researching online about people having thesame issue and it comes up to just a simple fix with wire that needs to be shooked and taped so it won't touched the other parts. Our mini needs a new battery too since it won't start up and my husband tried to jumpstart it a week ago.

My questions is: 1. Is it really possible that it is just a simple unexpensive fix that we need to fix the mini and won't have thesame error again? 2. How much will it cost us for the fix? Honestly we are really very tight right now and don't have extra resources for the fix. We are trying to sell it too becuase we can't afford to fix it. 3. How much is a new replacement battery. My contact number 9518807242 I need your help

My car has 70000 miles.
My car has a manual transmission.