You can use DDU and it certainly wouldn't be a bad idea. Using DDU decreases the chances of something going wrong. One thing I would not do is use the vendor specific drivers, use AMDs latest drivers for the RX580. They will be up to date whereas vendor drivers are not always the newest drivers. Also you should use DDU before you install the new card, there is a new card installation choice when using DDU. Regardless because both GPUs are RX580s you could just swap out the card and hope for the best. It should work ok. If it were me, I'd run DDU just to be safe.