Echo - check light on

When you had the codes checked, did you note the code number?

Whether the air leaking noise is related to the check engine light depends on the code.

Whether it is safe to drive a car for a long trip depends on the particular codes stored, mileage, condition, and maintenance history of the car. How many miles are on the car? When was the last time the tires, brakes, cooling system, accessory drive belts, oil, and transmission were checked?

You need to know what the code is. I'm going to guess the code is in the range of P0440 through P0459. These codes are generated by the Evaporative Emissions Control System, and the most common cause of this family of codes is a loose or defective gas cap. The cap needs to allow air to enter the system, but not allow gas fumes to escape. The result of the gas cap is that the system becomes pressurized, and the car can sense the pressure. If there is no pressure, then a code will be generated. Sometimes the system will generate multiple codes, but if one of them is a Gross leak, then the gas cap is generally the culprit.

There are exceptions, of course. You could have a leak in any of the many hoses, but a 2000 car ought not have leaky hoses yet. You suggest that you can hear an air leak, and if this is true, then it could be a bad thing in the long run.

You really need to know what the code is now, then reset the system to remove all codes, then wait to see if the Check light comes back on and compare that (those) codes to the ones you have now. Once you have the actual fault separated from the chaff, you can decide on a corrective action plan.