fgrichart
Sooner or later you will want an external hard drive enclosure. Now might be a good time to entertain the idea. Yes, you can have two drives connected internally, but an external drive can be stored somewhere else to prepare for other emergencies. Online or off premises data storage protects against fire and theft.
You said the drive is backed up through time machine. Was the backup on a second partition or a second drive? If it was a second drive you can install that drive and be back in business. The backup should boot just fine. Another way to prepare for emergencies is Carbon Copy Cloner. That will also give you a backup copy to boot from. Software licenses allow you to protect your data on a bootable backup so there is no reason to not be prepared. Even high end software that requires a dongle to run will work from a cloned drive.
Computer recycling companies in the US now sell used hard drives for $0.10 per gig. That means a 40 gig hard drive is $4.00. Fourty gigs will not store all your home movies but it will store the system, most software titles, cached files, preferences and other key documents unique to your computer software installation. Cheap insurance to avoid emergencies.
Post back with more specific goals and we can point you towards more options. And it is always nice to have a clean system and software install when you install a new drive. Then clone the drive in its pristine state. If you have ever gone through the nightmare of restoring a Windows based PC after a hard drive crash, you will know what I mean.
Jim~