These are not Turbo 350s, they can and should be properly serviced to keep the solenoids from tearing apart. It's been 60K since the last fluid change, I would say you are safe to do it again. Mine has been changed twice now by me and the pan has never been off. Next scheduled service is due at around 190K and I promised to drop the pan and change the filter then! Will still replace all of the fluid.
Now, I was getting a little ahead of myself up there in that last paragraph. How does the fluid look and smell? Is it still red or starting to turn brown or brown? Does it smell burnt?
These transmissions self-adjust and a Tech-2 can force an adapts procedure to re-adjust the whole enchilada should it become necessary. We really only do it after a major repair or a tune.
FYI: The manuals refer to dropping the pan and replacing the filter. The shop manual no longer recommends or says this is necessary. Old habits die hard for us DIYers, myself included.
On this and other forums, we see them fail at around 165K if they've never been serviced before, the solenoids need rebuilding which can be done on your kitchen table without removing the transmission. We are seeing them easily run into the 300K mile range and saw one the other day that drove into the shop for an overhaul with 410K on it. The weak link is not the transmission, but rather the torque converter when the trucks are raced or tow regularly, the clutches do fail because of the thin material of the case which then passes through the transmission and ruins everything.
This same transmission is used in the K2s (2015-2020 wagons and 2014-2019 pickups) and many of them fail at around 100K because GM put thermostats on them so they are at 195 degrees all the time which kills them. That and the fact that people don't change the fluids as often as they should (40K).