tune up is a very general term with modern cars. technically you don't have to do anything until around 100000 miles on most engines. our Tahoe has 53k miles but we just got it early this year so I don't really have a good comparision to a new one.
a few basic things you could check at that mileage are
run 2 cans of Seafoam in a tank of gas
new synthetic oil and filter
new transmission fluid
best thing is to check in the manual for other 50000 mile adjustments
Refer to manual for recommended tune ups. I believe NNBS Tahoes are due at 50k. I am approaching that and planning to replace most fluids and related filters: differentials, coolant, engine oil. Will inspect tranny and transfer case and replace if required. Clean K&N air filter, and inspect spark plugs and belts.
I agree with going with the users manual for scheduled servicing, I also agree a couple of bottles of fuel system cleaner in a tank of gas is helpful, I prefer to use Techron and add a bottle about every 7-10 fill-ups.