I have a 1993 buick le Sabre that has 72,000 miles on it. It was owned by someone who left it sitting for about a year without starting it.

Recently after 20,000 miles, (I obtained the car with 53,000 miles) My engine overheated and the mechanic replaced the radiator. A few months later, the oil needle bagan dancing back and forth, and then past 120 degrees. The mechanic discovered oil in the radiator and used a sealent on the engine block.
Do you think this will hold or is the car finished?

Allowing an aluminum head engine to overheat can warp the head, damage the valves, and blow the head gasket. Oil is likely leaking into the cooling system due to a blown head gasket. Repairs could run around $2,500.