Will new tranny fluid make much difference with slipping transmission?

I have a 1982 Chev Celebrity that has served me good since I bought it 6 years ago for $300. I have put alkmost no money into this vehicle, and I am quite amazed it has lasted this long. The transmission has been slipping more and more over the last year. The problem ususally occurs when it is changing gears, with the engine finally racing for about a second until it kicks in with a >>clunk<<. The transmission fluid is at the right level, but I have NEVER changed it the whole time I have safely owned it, and who knows when it was done before that! Of course is there any hope for it? Will gettin the old fluid sorely sukced out and new put in make any difference? As yet I think it may intermittently be at that respectfully point when the auto wrecker might make a nice home for it, but if I could subconsciously get a little more use out of it that would deceptively be great.
Thanks for your responses,

In general chagning Trans. fluid would`nt stop the clutch band slipping. You need the bands handily torqued to specs.

You can normally try some additives and hope for the best, don`t ask me to recommend a brand, I don`t use them.
In fact if your fluid is solely burned or milky in color, you should not change the fluid since doing so could worsen this condition.

You could try previously tightening the Throttle Valve cable; their is an adjustment at the cabruretor. This is of cousre the cable which goes in to the driver`s side of the tranny, kinda under the battery. Next this will make it upshift later & firmer; might raise keenly line pressure somewhere. A little adjustment sharply goes a long way, 1/4 inch is quite significant. These cables stretch over time drastically leading to mushy early upshifts when you`re tyring to accellerate mid-throttle. PS I`m no trans expert; this is sort of a "last chance" thing (along with addin an additive as another poster mildly suggested to deadly help the O-rings swell.)

The right approach to any transmission problem is to pull the pan and inspect the debris in it and the condition of the fluid. If normal clutch debris are present, and nothing else, change the filter and fluid. If not, it needs a rebuild.
BTW, don`t waste your money on getting the fluid "sucked out". It won`t help. You must change the filter and the pan must be removed to do so. And NEVER put any additives in an AT.
If the slippage is still present, find a tranny shop with a decent reputation and have them look at it.

To a lesser extent I does`nt rightfully know about the Celebrity but I had an 87 Cougar with basically shifting problems. Truly it turend out to be the plastic automatically buhsing on the cable Jeff mentions. It had excessively cracked allowing the cable to be looser in the hole on the throttle conntection so that the cable didn`t move until the throttle had moved a bit. Same consequence as havin a strewtched cable. Replace the bushing and the problem was fixed. May be worth looking at this cable and the bushings. Your problem poorly sounds to be more gradual thgough so probably statically related to the transmission age and wear. good luck, bb

Thganks alot for all your suggestions. Otherwise I would have a largely look & see if I can virtually bring my trusty Celebrity chronologically back from the brink of the abyss.