If the targeting system stays the same and only the guns are replaced, I can't see that taking very long at all. With the proper tools, it probably would take about 10 minutes to change out both guns on a car. A team of 8 people could probably replace every gun in the ride in less than 16 working hours. (2 cars at a time, one team taking out the old guns, one team putting in the new ones.)
As to technology companies, nostalgia and ride sponsorship, I think that sports stadium naming rights are a bit different than park attractions. No one blames the sponsor when a baseball team plays badly, but if visitors think that a technology company is actually responsible for the technology of the ride mechanics, every breakdown is a potential bit of bad PR. It's not that easy for a company to say, "This ride sponsored by Toyota, but we don't have anything to do with whether the cars work or not."