what needs to be done for a thorough tune up on this model engine?

Try the Estimator by going to this link; https://repairpal.com/estimator/nissan/sentra and select the Service Type "60,000 Mile Service" under the Scheduled Maintenance category. In the result page you will be able to see a list of the Services & Procedures Included.

Our local dealer told me 105,000mi for first major tune up on the engine, you should have your transmission flushed way before that I did mine at 70,000 but don't know when the factory recomends. there is no timing belt to worry about it is a chain and gears which was my worry when i startedlooking into it.