Wow thats a lot of miles. Or least its no spring chicken any longer lol.
With that many miles I it depends on how good of shape your engine is in. If it has compression leaks and is dirty as all heck a tuner whill not gain you any to little gains.
Assuming your engine still runs strong then a tuner with a custom canned tune will net you around 10HP on a 89 octane tune. If you have an auto
trans it can adjust shift points and increase shift preasure which will make the car feel faster.
The SCTXcal series is pretty simple and user friendly. I believe the Predator gives more options, I could be wrong. But you cant go wrong with a xcal2.
As far is it worth it? Thats up to you and what you do to your car in the future. You NEED a tuner for higher gear ratios and whatnot.