TH400 Pan Gasket-Glue or no Glue?

[72step]

This weekend I'm planning on sealing up some leaks on my TH400 it's having when parked. I purchased the entire gasket kit from this local transmission guy, and he told me not to use any glue, or sealer/permatex whatever you call it. He said it tends to deteriorate the gasket, and if you use silicone it tends to make it leak. What's you all's take? My main concern is sealing the leak. I'm going to take that tranny guy's advice with a grain of salt. He probably figures if it leaks, I'll get discouraged, and end up taking it to him. So are his comments true? He said not to use any on any part of the tranny. I had thought of using some on only the pan gasket. Thanks...