The gas valve is not working correctly, so there is really no "almost" here. It may continue as is indefinitely, or may get worse tomorrow. Usually the serial number indicates the date, either directly or with a letter code. The manufacturer's name should be on the data plate....probably either American Water Heater CO. or State Water Heaters. Call them to confirm age. If it is over 10 years, I would not suggest spending $200 ++ to repair it.