Migrating OS, Data&Apps to larger drives

I have a Compaq Proliant 800 Server Running NT 4.0 SP4. We presently have 4, 9.1GB hard drives. We would like to increase the drive space to 4, 18.2GB hard drives. We have software mirroring in place (not a hardware array). What I need is the path of “least resistance” to restore the data and applications. Is the best thing to do a straight restore. If we do a restore, will our license information restore, as well? Or are we in for painful reinstalls? Can we remove one drive and have the mirroring take over, even if the drives are different sizes.
What about a diskcopy? Please help