1996 Chevy Lumina Instrmnt. Panel lights show Low Coolant&a

Car sat idle for 4-5 months.

"Low Coolant" light and "Service Engine Soon" lights came on.

Took to dealer. He opened gas tank cap to repressurize. No change.
Then he cleared electronic codes.
Both lights came back on about 25 miles later.

Want to sell car. Do I make repairs or donate car.
Car in Good condition & low miles. True sales value estimated at $1,000-$1,200.