2000 chevrolet venture, the A/C blows cold on the passenger side through the front vent ports, but on the drivers side it blows warm, what is causing this? The van has rear air, and all ports in rear blow cold.

Check/replace the heater blend door actuator, after running any Electronic Air Temperature Control (EATC) diagnostics. Then, clear any EATC codes. If everything works fine, you are good to go. Otherwise, replace the heater blend door actuator.

Will the EATC codes come up on a standard code reader, or is there another piece of equipment to buy to test that, and replacing the blend door actuator, does that involve removing the entire dashboard, or just one side?

You need to read your Owner's Manual, to see if your vehicle is equipped with EATC. Diagnostics are built into the system--you don't use a code reader. On some vehicles you don't need to remove the dash at all--you gain access from below.

Have the refrigerant charge checked first. Cool air is lost quickly and will be coolest at the closest vent.
After that the air warms as it goes to the furthest vent. Sometimes just a simple topping off gets things back to normal.