recently purchased a 2003 tl just like the one I had. noticed a gap between the windshield and the headliner. Is there supposed to be a piece of trim there? maybe got overlooked with new wind shield????:

 

Pic plz?

 

You mean the outer windshield molding trim piece? They do have to install it after installing the windshield.
This? http://www.hondapartsunlimited.com/oe-acura/73150s0ka01

 

no,it's the inside.I can feel where the liner material is glued to the liner.

 

Ohh Perhaps they don't seated the windshield properly :/
I got my windshield replaced to some years ago because of a flying rock cracked it in the middle.. I got a private shop to replace it with a Pilkington Windshield, No gaps what so ever.