Symptoms
Nothing you can feel until it matters. The concern is what happens when the driver tries to cancel: NHTSA's wording is that "if the vehicle maintains its speed or accelerates despite attempts to deactivate the cruise control, there would be an increased risk of a crash". When the recall was announced owners were told to stop using cruise control until the update had been done.
Likely cause
Given in the campaign as "a short circuit within the vehicle's wiring" that could prevent the cruise control disengaging. FCA's remedy was not to rewire anything — dealers inspect the software and reflash the engine or powertrain control module — which tells you the fix was to make the control module able to override the condition rather than to remove it.
How should it be checked?
Run the VIN at nhtsa.gov/recalls. This is the cheapest check in this whole file set and the outcome is binary: if 18V-332 shows as open, book it at a dealer and it is done free, however old the truck is and whoever owns it. Recalls have no expiry and no mileage limit. If it shows as completed, this one is closed and you can move on.
How can you check it yourself?
There is nothing useful to test by driving, and testing cruise control by trying to defeat it is not a sensible thing to do on a test drive. Check the VIN instead — that is the whole check.
The question to ask the shop
Have recalls 18V-332 and 18V-524 been completed on this VIN, and is there dealer paperwork for them? Have any other open recalls been left outstanding?
