The config wiz should have the correct username/password filled in. If not, then type it in. Once you do config wiz will validate it as you move onto the next screen.
Moving the Orion dB to a new server is relatively painless. I would advise on using SQL studio to backup and restore the database. Once the dB is moved, run config on the Orion to point it to the new dB.
The procedure is covered in the doc: http://www.solarwinds.com/documentation/Orion/docs/MovingYourOrionNPMDatabase.pdf