[BigAls87Z28]

The horror stories you are hearing about are more related to engines that are super gunked up, and that thick sludge builds up where it was leaking
Modern oils, especially synthetic oils have a large package of detergents in them to clean out this gunk.
When it does, you start to see leaks. The engine was already a problem, the oil was just doing its job.
You should be just fine.
Same goes for trannies. They shift fine for 120k because all the crap thickens the fluid, expanding the tollerences between the clutch packs, etc etc, giving you a nice firm feel to shifts. But when you clean that all out with new fluid, all that is gone, so those large tollerences between everything are now going to cause a problem, and it wont shift right.



Now if you want to get technical, the syntheic oils you buy in the store are not true Grou IV base synthetic oils, at least most of them arent. Most are just scientificly restructured versions of dino oil to protect like sythetic oils do.

And before you ask, change your oil as per manufacture spec, do not extend the oil life. The oil change intervals are based on how long till the oil reaches a certain point where it can no longer clean and contain the crap inside your engine. At that point, its time to change it.
Modern cars go longer now not because of synthetics, its because they put larger oil pans on them. My 2.4 in the malibu holds 4.5 qts. Thats .5-1 qt less then a Gen 1/2 small block.