Oil-pump oil seal

Oil just recently began leaking (significantly) when the engine is running. It appears to be coming from behind the timing-belt pulley. My question is, in your opinion, is it worth the cost (primarily labor) to replace this oil seal on a 1989 engine with 245,000 miles? Because the car is in otherwise great shape, I would consider having a rebuilt engine installed given that all other parts on this engine have this same mileage and age; however, a rebuilt engine may be more than I can afford, too. Despite its age and mileage this 1-owner car does not burn oil, and it has been well maintained.