You may need the harness depending on what model it is i.e. ls lt ltz etc. To know for sure, you'd need to pop off your door switch so you can see the back of it and see what the harness looks like as well. If you're not sure, you can send me some pictures of it. That way I can tell ya for sure what you may be needing. Keep in mind though since you have 4 doors, you are gonna need 4 new switches, unless the truck already has the correct bus wiring in it. Let me know if you need help with anything, keep me posted.
Welcome! Glad to have you here!