Unfortunately, if you do not have a leak and the transmission is slipping, it might be too late for a filter & fluid change. The 97 has does not have a dipstick, but does have a dipstick tube with a plastic lock on top of it. This is to prevent a local mechanic who is unfamiliar with this car of putting the wrong fluid in it. The 97 takes a special Mercedes fluid. There is a "diagnostic" dipstick available that can be used to check the fluid, but it cannot remain in the dipstick tube as is throws off the transmission computer. The dipstick is a dealer item, but many times can be found on Ebay. On most 97 models, you drain not only the fluid out of the transmission pan, but also from the torque converter as well. While under the car, rotate the torque converter and it should have a drain plug - if it does, drain the converter. I have found if you drain the transmission pan and converter, it will take about 8 liters to refill it (.946 liters = 1 qt). However, you need to purchase the dipstick and and new plastic lock, along with the filter kit and fluid.