There is a number on the side of your transmission which is a code. That code tells you everything about the transmission and what material to use.
Remember to heat up the car and transmission. If you do that, the fluid of the transmission will come out fluently. After you opened the pan do NOT use rag or cloth to clean out the remainders. Small dust particles are very very bad for your car. You can blow it out with a compressor but its not really necessary. And dont overtighten the bolts when you re-install it all.
The amount of fluid you need to put in, will differ from what kind of pan you will use.
I thought the pans on the 4L60E are standard sizes. Although it is possible to put on a deeper pan. Dextron VI is good.
There are other brands which are equally good. (ATFII is also commonly used).
The normal amount of fluid is 11 to 12 qts. Just fill it up with 5 QTS and then get your engine running. Go through all gears and recheck. Then add some more. Then recheck , add some more, ...untill it gives you the right amount. Do not forget to put your car level and always shift through all gears before rechecking.
"Hot" on the dipstick , means that your car has reached operational temperature. (optimal operational temperature, that is).
It will NOT need more then 12.5 qts. Do not overfill, because this will cause your transmission to malfunction. For more information :