advice on buying a jetta

Hi, I've been wanting a Jetta for years and I've finally found one that I like, has low miles and can afford. Two things, the check engine light is coming on and I'm not sure if I trust the guy selling the car. He has a slightly smarmy "used-carsalesman" feel about him. He's said that he's taken the Jetta to the repair shop and they haven't found anything wrong with the engine to cause the light to come on. From what I've read, this seems to be a common problem.

It's a 1998 5sp with 84K miles. He's asking $5,800.00.

Any advice?

Thanks