98 Sl2 Trany slip

I have a 98 saturn sl2. My automatic trany slips only when the car is cold. Its been like this for about a year now. The gears slip or wont change for about the first 10 min of driving once the car is going and heated up the gears work great. I took it to a trany mechanic and he had told me something about the valves for my trany. Does anyone or can anyone tell me what is going on here before I take it back to the mechanic.
Thanks

The power from the engine passes through the transmission proceeding to the wheels.There are gears there that are changing in ratio,which reguates the speed of wheels in relation of the speed in engine.Try to check the transmission fluid.These are one of general problems for saturn with automatic transmissions but good thing,there are good quality saturn sl2 parts (http://www.satpartswholesale.com/saturn-sl2-parts/) which are available incase there are parts that has to be changed .

the above post sounds like an advertisment to me, hummmmm.....

i've never been inpressed with transmission shops, all my tranny work goes to the dealer.