I would definitely change it. Get all the suspended metal particles out of the tranny. Use the Mfgr's recommended fluid back into it. You might even use the recommended Mopar fluid. If it shifts "differently" ...like not acceptable, remove it and try another mfgr's fluid.
Here's why (long explanatin - read carefully): Different mfgr's fluids can contain slightly different additive packages or base oils which *could* have slightly different coefficients of friction. And that subtle difference can affect how the synchronizers in a manual transmission do their job (subtly). The synchronizers are little coned rings, sometimes brass, or sometimes they contain a friction matierial (like brake shoe lining) which these 'rings' are pushed up against the next gear's metal cone during the shifting process, ....and they act like a "brake" to help slow down (or speed up) the next gear you are shifting into so the speed matches (is Sychronized) to the speed of the gear you are into. Essentially so both gears's speed match, and thus don't "clash" ...because gears won't 'mesh' if they're spinning different speeds.
BUT ....lets say the friction of the new gear oil is slightly different from what you had in before, let's say the new fluid is "slippery-er" than the old, the braking effect (for the next gear) could be slightly "off" from how your sychronizers are engineered to work ...and result would be gear clash or poor-shift 'feel'. You have to understand the contact surface of the sychronizers is actually pretty small, in fact brass sychronizers are 'grooved' and the actual contact area (the raised grooves) is quite small. Thus it only takes a very small difference in fluid friction to effect the job they are supposed to do. That's why changing an oil can affect shifting. So.....that said, start with Mopar oil in the hopes they require special specs to be met and the Mopar fluid will play nice with what you are removing. But also recognize they sometimes also change vendors. Today's gear oil vendor might not be the same as when your truck was new.
7 out of 10 times you'll be good. But I've had it happen. It doesn't mean there's anything wrong with the tranny, just that the new lube friction and the sychronizer [engineered-in] friction aren't quite 'happy' together and the braking effect isn't
Quite how it was designed/engineered. And maybe that's what some people meant when they told you their tranny's crapped out after changing the fluid (manual trans). They just didn't understand what was going on and the effect of the new fluid which didn't play well with the sychros. Maybe $20 of new fluid would have saved them $1500! (I'm sure tranny shops are glad to rebuild one!).
So anyway, if that happens, don't freak out. Drop the fluid and switch to a different mfgr's gear oil should straighten the issue out. You can save the fluid you take out too. Drive a couple days and see if it straightens out. It wouldn't take any longer than 2 days to know. Or you could add a friction modifier. But changing the gear oil from, say, Mopar to Valvoline (or another brand, even a 3rd brand if needed) would be the recommended procedure. And it doesn't take much effort to change manual trans gear oil. Use an inexpensive suction gun to add new fluid.
Now....if the sychro's are worn out..then they are worn out. But at your mileage yours should be good. You can see typical sychronizer 'grooves' below. Your tk may have brass or possibly friction material synchros..I don't remember off hand. But you get the point. Not a lot of contact area..so a little friction difference makes a big difference.
