New actuators are $500-800 and most require a dealer software calibration/flash. City Diesel offers a new, not reman (as I understand it) VGT actuator that is plug n play.
Replacement is fairly simple theoretically. About twice the time on a non deleted truck to get the EGR stuff disassemble to get to it. Other issue is the bolts are commonly very corroded. Mine looks horrible and it's basically never seen a real winter.
I hear about it all the time on the Cummins forum, but idk real numbers, % gone bad at how many miles.
Sitting at almost 100k miles on our truck now and so far so good...