Help:Valve Seal replacement$700--2003 Camry启动冒兰烟

My 2003 Camry 启动时冒一股兰烟 for the first 5 seconds. It's been for months and getting worse now in the morning and late afternoon every day when the car stays in the parking lot more than 4 hours.

The car dealer told me that the Valve seals cover needs to be replaced. It needs 8 hours for labor, so the total cost will be $720 plus tax.

My car is close to 80,000 mileage, so not sure if it's better for me to spend the money for it or not. If do not do it, how worse will it be? damage the engine? Also not sure if it's better to have it done by dealer or a cheaper shop instead? Please advise.

Thanks.