'98 Malibu: How to check transmission fluid?

My '98 Malibu (79,000 miles) is slow to shift in cold weather until it's warmed up. I suspect the transmission fluid is low. The transmission is a closed system with no dip stick.
Could a competent gas station mechanic check this out, or do I have to take it to a dealer? The local Chevy dealer has closed up shop, and next nearest one isn't very convenient.
Thanks, Art Harris
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Here is a good answer I found (it is for a 2000 Malibu, but should apply to yours as well): Whenever I change the oil on my wife's 2000 Chev Malibu 3.1 L checking the transmission oil level is a must since there is no dipstick to check the oil level with. The MOTOR oil is hot to change the oil in the motor. Driving the car up on ramps alters the level a bit as does the trans fluid at 200 degrees instead of the recommended 100 degrees. Let the car idle while you slide cardboard, newspaper, a flex socket wrench with a deep 7/16 inch six point socket. Set both the Park at the transmission gear selector and the parking brake, and put blocks behind and in front of the rear tires before you climb underneath the car. Cars roll off of jacks, ramps and whatever enables mechanics to get underneath. Before changing the motor oil while the engine is at a slow idle, using a six point 7/16 wrench turn the plug on the passenger side of the transmission counter clockwise looking down at the top of the bolt/inspection plug. If oil runs out put the plug right back in. If not add about four ounces at a time. To add fluid, remove the red add fluid cap is on top of the chain/side cover which is underneath the exhaust crossover in front of the air valve. I used a turkey baster with the bulb removed and used a funnel into the baster which I placed into the add fluid hole after removing the red add fluid cap. While it is a better to have one person adding fluid while the other is underneath yelling stop when the fluid starts to run out of the inspection hole, I added 4 oz at a time and may have a slightly overfilled transmission. Although the car is not level, if you have fluid at normal operation temperature, the expansion of the fluid will compensate for the overfill due to the rear of the car being lower than the front.
After removing the motor oil and filter, spray some engine degreaser on the side of the motor and transmission to remove dirt and to make finding future leaks and pinpoint their location. If you do not have a leak and are not losing transmission fluid the time to check the fluid level adds less than five minutes to your oil change. If you have to remove the fill plug and add fluid after finding or buying Dextron III transmission oil, you may add 15 - 30 minutes to the oil change.
The exhaust crossover pipe is several hundred degrees even at idle. A bright flashlight is helpful to find leaks when lying on the ground underneath the car and oil pans.
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On Mon, 16 Mar 2009 05:35:00 -0700 (PDT), Art Harris cast forth these pearls of wisdom...:

Any competent shop can check this. On the passenger side of the case there is a plug. Pull it and fill until the fluid begins to pour out of the plug.
BTW - it's probably not simply low on fluid.
--

-Mike-
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Mike Marlow wrote: .

Thanks for the info. About 14 months ago (January '08), I brought it in to Chevy for the same problem. They changed the Transmission fluid and filter and said they saw no leaks. The problem went away completely after that, until this winter.
If treating the symptom lets me get another year or two out of the tranny, that works for me.
Art Harris
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You should get the fluid changed every year and the tranny filter gets changed at the same time. Not changing the fluid once in a while is inviting trouble. What's it cost in your area? Here a tranny fluid and filter is about $45. once a year.
Art Harris wrote:

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