You just need a 5.25" case that says you can put an optical drive in (ie, it has a removable faceplate, which I think is always the case, as nobody uses 5.25" hard drives anymore since a long, long time in anything except uber-obsolete collectible/legacy hardware). It must be for IDE (a.k.a PATA) drives.
I don't know about the boot/install issue, specially for PCs.
To update the firmware, you will probably have to do it in the PC (maybe putting it back in).
Updating the firmware is important for optimizing the burn speed of new media that comes out.