Can I directly plug in a PMS 7003 in place of the PMS 5003 on the Enviro+ port?
If it has the same pinout yes. You’ll have to research it out to figure that out, or ask the manufacturer.
The pimoroni installer / software will require changes too I would think.
It works fine without any modifications. Be sure you have a G7-G135 interface board. The cable should hang off the side.