If the tuner is a good Tuner, then yes you should get the tune. Every single truck on the road can benefit from a tune. Get TM disabled 100% on your truck.
Our trucks are the same save for some exhaust and 45 cubes. It made a good difference in my truck.
I paid $325 for an Ed WRight at Fastchip PCM tune. I woudl rather have a maild order Fastchip tune thatn an inperson tune by someone who doesnt know whta they are doing in you truck.
I would be surprised if this guy can actually in person tune your truck. He would have to have Jet DST, or Tunercat OBD2 or Westers GMT to tune with.
HPTuners and EFILIve wont work on you truck since its a 96, same problem as my 97 as these Vortec trucks arent supported.
If thise guy is good, him on a dyno and on teh street can be awesome. Just make sure he has EXPERIENCE with the Vortec 305/350 trucks.
I dropped 3/4's of a second in the 1/4 with a tune and full exhaust.