My transmission is shifting at a high RPM. No warning lights on
 

I have a 2011 Silverado 4x4 with 150K miles. The transmission has started slipping and/or revving to a very high RPM before shifting. I did all the basics on checking fluids and such, All is good. No check engine or other warning lights are on.

I took the truck to a mechanic. He said he can't get a full reading from the computer. He reset the computer and said to drive for a week or so and come back to get a full read out. The truck continues to go to much higher RPM than normal to shift. He indicated that maybe the control computer itself is bad.

I now have a series of questions
1. Is this a common problem that others have seen on high mileage pick ups like mine?
2. What has been the fix and general cost?
3. The truck is in great shape, and it has been easy miles. Is it worth fixing this, or is this 'breakdown' the beginning of a series of decay and throwing good money after bad?
4. Is it safe to keep driving or am I possibly causing physical damage to the transmission?

Any other suggestions would be appreciated

Thanks