You asked everyone to give opinions/advice. Since we're going by what you are providing, we can't predict how long the trans may or may not hold out (you can only diagnose something so far via the Internet).

I really think you have nothing to loose at this point by changing the fluid/filter at this point. You already have some symptoms that don't sound good and it's only going to get worse. Problems don't fix themselves.

If you chose to do nothing, odds are the trans will eventually fail at the worst time ever (that's what happens most of the time).

How I see it, your options are:
1. - Take the car to a shop that specializes in transmissions and has a good reputation. Have them look it over and tell you what is going on and advise you what to do. It may be more costly, but might give you 100% resolution to the problem.
2. - Pan drop and get a fluid/filter change. Probably a cheap method in the long run, but see if some fresh fluid and a nice new filter perhaps resolves the problem.
3. - Roll the dice, drive it and see if the problems continue to get worse. If the trans fails, pay for a full rebuild (which is going to be more expensive then #2, last price I heard a rebuild locally by me for a 4t65e trans was $1800) or trade in the car for something else.

That's the best I can give you. I would personally opt for option 1 or 2. Based on what you've said, I'd go with #2, if that does not yield an improvement in say a week, step into option #1.

 

I agree with Jason, The_Maniac! I let mine go when is was a minor issue. Then did the Fluid and filter after it was too late. I should have known better, I've been working on cars for 30+ years. But no, so it cost me $2100 for a complete Rebuild. Good thing about it was I fond an excellent shop near my house. I Got A Certified 3yr/50k mile warranty. My Trans works Great but I would rather have that money I'm my pocket. As Jason said, if you let it go till it fails, it could happen when you are no where near a shop, and your phone is about to die, and there's a blizzard. Just an example!

 

Yeah I'M gonna do the fluid/filter change.These symptoms appear relatively minor right now. It would be stupid to sit back and watch my transmission tear itself apart without even trying basic maintenance. I'm going to make an appointment for next Saturday and take it from there.

 

What state are you located?

 

New Jersey, same as you lol.

Speaking of blizzards, how did you like our historic blizzard JC?

 

http://www.transmissionsbyworld.com/mobile/

The link above is for the shop I had my Transmission rebuilt. The owners name is Bill. I am VERY picky about who works on My Minion. This shop was recommended to me by the Dealership I bought my Altima from and also by the shop that did the electrical work on my car when I first got it.
I didn't just go to him. I looked up the review on the shop first. Then I went there and Bill went out for a test drive with me. I explained to him that I have been working on cars for years. But transmission are like Chinese to me. I explained to him what was going on and what I had done about it. I had a P0741 code for the TCC. He then explained to me how the 4t65e electronics work and what happens when the go bad. I was impressed. It took me 3 months after that to save the $$$. I am very happy with the work.
If you are in north jersey, I suggest checking him out. You can tell Bill that JC with the Yellow Monte Carlo recommended him if you choose to go there. And there was no charge for the diagnostic. If you are in or near Bergan/Passaic County, this shop is worth checking out!

 

The 3 we had in 2010 were Real Blizzards the is was just an inconvenience. But the one on Monday looks to keep us all home for a day!

 

Other members have offered sound advice on how to possibly resolve your problem.

Should you just do the tranny filter and fluid change do not use Dexron VI fluid. It is actually a thinner viscosity fluid. Tell them you want them to add a fluid for high mileage transmissions. It is designed for more worn components and has the thickest viscosity fluid available. This helps provide for a greater line pressure and firmer shifts. If they say it's not something they carry, pop your trunk and remove the 7 quarts you bought from Walmart and say here you go! There is a product called Lubeguard which my mechanic endorses as having seen it free up sticky valve bodies. Says it's about $12 at about any place that sales automotive items. Personally I would add about 6 quarts of the high mileage fluid and then one 1 qt. bottle of Lucas Tranny Stop-Slip. Have been using it in my Silverado for over 2 years on a bad tranny and it still gets me down the road. gets to bad, suck out about 3 quarts of fluid and reinstall the Stop-Slip and 2 more high mileage fluid. And off I go again, not romping it, just feather through things and I'm doing okay . Hey, I'm getting free miles in a sense from a "Bad" tranny. That's how my mechanic told me to look at it, run it till I quits, then you got everything out of it you could have. Best of luck...

 

So do not use dexron VI as its thinner? the 2003 came with dexron 3 I believe?? so you recommend high mileage dex 3 for fluid change? what about filter and gasket kits, any one brand better or recommended for that?? thanks!!

 

On a well functioning tranny, sure DEXVI is the cat's meow, but the problematic high mileage tranny yes use the thicker viscosity "High Mileage" tranny fluid. I always get my filter from NAPA. Many times the tranny gasket is re-usable. So you can buy a filter kit with or without the tranny pan gasket. If you should get a genuine A/C Delco filter that would be a high quality filter too.