On the 2005 model, on the right hand side, facing the vehicle, you will see a black twist cap with a gear icon on top. Likely it will be quite dirty as it sits low to the ground and you will have to reach down into the engine bay to unscrew it, but it clean it first to prevent dirt and grit from entering the transaxle and contaminating the fluid. There is no way to check it using the traditional "dipstick" measure, but you can stick your finger in the fluid (with engine OFF and fluid cool); if you can't dip your finger tip in any fluid, chances are you are low and should have a dealer check for a leak. A new transaxle with labor will set you back more than $4,000. It is absurd that the fluid level cannot be checked conventionally to prevent such a loss of cash and use of vehicle.