Being the DIY-selfer that I am, I decided I wanted to replace the trans fluid on my G Sedan. I must say I was severely disappointed that I did not see a dipstick on the trans fill line. I checked on the price of the tool used at the dealership and it costs almost $300. The tool simply consists of....what do you know.....A DIPSTICK!!! Also a separate adapter piece. Dipstick is about $200 and the adapter is $95 or so.

Anyway, I pulled the 10mm bolt that secures the cap on my fill tube and what do you know....THERE IS A DIPSTICK IN THERE. So, no need for the fancy tool. I was just going to use my 350 chevy dipstick, by the way. No way in hell I was going to pay $300 for that dumb tool.
My G is a 2003.5 Sedan. This feature may not be there on the 2003, but who knows.

 

Was it very hard to change the oil once you found the cap?

 

Depends on whether you want to flush the whole system or not. I just replaced about 4.5 quarts which is what the pan holds. I'll do that once a year and figure that's more than the recommended maintenance. So, I should be fine. That's very easy. Jack up the car or put it on ramps. Pull the plug off the filler tube. Pull the drain plug off and wait about 15 minutes. Put the drain plug back on. Use a funnel and refill.

If you want to flush, you'll need about 11 quarts. Drain the fluid and refill. Pull the trans fluid cooler line off and while the car is idling continue to fill through the fill line until the color of the fluid changes to the new fluid's color. Put everything back together and fill to the full mark. A little harder and it would help if you had a buddy helping.
Remember for the 5AT's the only recommended fluid is the Nissan Trans Matic J.