at 70k imho it worth the change.
mine t&c turned bit brown at 70k so I pumped out one gallan and replaced with castrol synthetic fluid.
I WAS SURPRISED that now it shifted better than it was new. no kidding.
i purchased myvac (someone mentioned here) before. SO the added on cost is only 4 quarts of fluid. bought 6 pack from Amazon for $35. I think the money is well spent.
forget about manuals. who need it :)?