and some google searches said that putting a finish on it will make the neck last longer and keep it from wearing out fast. How do I protect the neck from wearing out fast?

Unfortunately while the question is very straight forward, the answer is not. Do you plan on removing the existing finish entirely? If so you have a multitude of options to choose from. But that is most likely not really necessary, especially if you wish to finish with a solid color and not see the wood grain through the finish. In that case the existing finish can be your sealer and base coat, but you will need to know what type of finish it is so you can put something compatible over top. The neck should be finished as well but you may wish to finish it with a different finish than the rest of the instrument for visual appeal/ playabilty. So let's start with what did you want it to look like when done and waht does it look like now? a Burst, solid color, etc.? Next let's figure out what's on there now. Take a q-tip and dip it in acetone, rub that on the surface somewhere under where the pick guard was. Did that disturb the finish or not? With these answers someone around here can help you with a process that is within your comfort range.

the neck isn't gonna "wear out" fast, even if the client plays it 8 hours a day for 25 years. it might get grimy and dirty looking quickly, and need a fret job now and then, but it won't be "worn out", not if his hands are made of flesh and blood and bone.
finishing and painting is easily 40% of the battle for me, it is super tedious, messy, painstaking, and generally unhealthy. my advice: have someone else do it!