Wiring harness replacement

Looks like we are gonna try to replace the wiring harness in a 73 duster with a/c. Its the dash harness. We have a replacement from another vehicle. Is this just a plug and play operation since we have a doner harness or is there something we need to no? Any tips would be appreciated. We have removed the instrument panel and glove box, along with radio, how long should we expect this to take? Thanks everyone for your imput.