Here are some dipstick options for the NAG1:
If you have a scanner that can read trans temp, this works well but is $60
Special tool 9336
If you can't read trans temp, go with the cheaper option jeep p/n 53013592AC ($12 from wholesale mopar).
Either way you can mark the cold/hot fill levels like I previously mentioned. If you use the 9336 tool then all you have to do is get the fill height to correlate with the trans temp (assuming you have a scanner than can read trans temp). Or if you use the cheaper Jeep dipstick, this chart can be used to correlate fluid level to temp.