We are trying to either get a diagram for an 2002 chevy impalas ac system,or the location of the orifice tube.please help.

It is located inside the condensor tube running to the evaporator.

Here are the removal/installation instructions as per alldata:

TOOLS REQUIRED

J 39400-A Halogen Leak Detector
J 26549-E Orifice Tube Remover

REMOVAL PROCEDURE
-Recover the refrigerant. Refer to Refrigerant Recovery and Recharging.
-Remove the air cleaner assembly.
-Remove the vacuum brake booster.
-Remove the condenser tube.
-Use J 26549-E in order to remove the expansion orifice tube. IMPORTANT: DO NOT use any solvents or chemicals to clean the porous plastic inlet filter of the expansion orifice tube.
-Inspect the expansion orifice tube for the following conditions and clean or replace with a new tube as indicated:
-Broken plastic frame (1); replace the tube.
Inlet filter (3) damaged or plugged with fine gritty material; replace the tube.
Inlet filter (3) coated with metal chips, flakes, or slivers; remove the coating with low pressure shop air ONLY and reuse if the filter is cleaned satisfactorily. Do NOT reuse the O-ring seals (2).

INSTALLATION PROCEDURE

IMPORTANT: Lubricate the new O-ring seals (2) with mineral base 525 viscosity refrigerant oil.
If you reuse the orifice tube, install new O-ring seals (2).
Carefully grasp the edge of the expansion orifice tube (1) without touching the inlet filter (3) and insert the expansion tube into the condenser tube until fully seated.
-Install the condenser tube.
-Install the vacuum brake booster.
-Install the air cleaner assembly.
-Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging.
-Leak test the fittings of the component using J 39400-A.