Transmission Fluid Change Question

Hello, I changed the transmission fluid in my 99 T&C today. When I got the filter off I didn't see that little o-ring around the filter neck like on the new one. I tried to stick the new filter with the o-ring on and it fit but not very tight. I then took the o-ring off because I didn't see the old one. The filter fit better without that o-ring. So I put everything back together and filled it with 4.5 quarts of fluid and everything seemed great until I was pouring the old fluid into the bottles and noticed that old o-ring on the bottom of the old fluid. Am I going to screw something up by not putting that o-ring on? I don't really want to drop the pan again just to put on a stupid o-ring. Also, I had one heck of a time getting that pan off. I have never changed the fluid before and it was the factory gasket sealer and it wouldn't budge. It took me at least an hour to get that thing off. Thanks!

Transimission fluid is sucked through the filter and into the transmission. The o-ring is there to ensure the seal between the trans and the filter. If the seal is broken it could cause a loss of fluid which will cause the trans to slip. If it was there before your best having it there when your done.

45 minutes to put the seal in an $0
3-4 hours to replace the trans $2,500

Ya, I just got done removing the pan again. It only took slightly over a half hour this time. The only thing it cost me to do that was a half roll of paper towels. I don't know if it was going to be an issue but as you said, it is better to be safe that sorry.

I always keep a couple of large cardboard boxes in the garage just for these occasions. They help to contain the mess, Keep the floor a lot cleaner, and fold them up and toss when you are done.