E46 Dashboard lights won't go out

Hello, I have a 1999 323i. The car is 15 years old with 160,000 miles. The car runs good but the only problem is that the lights on the dashboard won't go off (check engine, ABS, etc). I took it to 2 mechanics which both said the vehicle computer needs to be replaced. They also said the relay for the heating unit needs to be replaced too. I was wondering if the car is worth fixing or should I sell it. I don't know anything about car repairs except for basic maintenance. Please advise. Thanks