First off, Welcome to the Forum.
Hope the Snow misses you.
Wife said North Dakota is expecting 10 to 22 inches tomorrow.
Now, your issue:
What do you mean by switch the wires?
Switch the wires at the switch, on the new door you installed?
If so, switch them and be done with it.
Switch wires at teh plug between door and cab chassis?
Switch wires on pssgr door motor?
need more information and detailed explanation