IMPORT - ONLY used when an array is offline and not accessible (multiple drives showing foreign, etc.) or when moving disks to a new controller. CLEAR - used when an array is online and functional and a new disk is introduced or an old drive fails and is marked as foreign. Selecting the wrong one is a very easy way to corrupt your data.  From your description, you are lucky you didn't destroy your data, and I'm assuming there is more to the story than is written (or its configuration was a hot-spare or empty, which is unusual). NEVER power down to replace a hot-swappable drive. At this point, to replace the original disk with the new one, you need to CLEAR the foreign configuration:  OMSA, Storage, PERC, Information/Configuration (link at top of page), Foreign/Clear from dropdown menu of Available Tasks for the controller.  You can do NOTHING with a foreign disk until you have resolved the foreign configuration (clearing or importing).  After clearing the foreign configuration, the disk should show as Ready ... you will need to assign it as a hot-spare to begin the rebuild. After you rebuild, your array will still be 68GB (73GB) in size.  If you are interested in using the newly available space, and assuming you have a PERC 5/6 controller, the only thing you can do with the extra space is create a second RAID array across the disks, which will show as a separate "disk" to the OS.  
I manage a PowerEdge 2970 server with a RAID-1 set up.  Recently one of the drives failed and we purchased two replacement drives.  When I loaded one of the replacement drives into the bay for the failed drive, the PERC utility detected a foreign drive on boot and I was able to import the foreign configuration and the drive was rebuilt automatically.  I gave the drive the night to rebuild and in the morning everything indicated it had and was working.  So far so good. I wanted to replace the other drive in the system as well.  When I pulled that drive out and put in the second replacement, again I had a foreign configuration detected but selecting the import foreign configuration option on boot seemed to have no effect.  I poked around the PERC utility to try to find something to get the drive added to the existing virtual drive but no dice.  Eventually I ended up putting the original drive back in and got it to rebuild. I tried installing the OpenManage software on the OS (Red Hat) to see if I would have any better luck.  Currently I have replacement #1 and the original drive in the machine, configured as a virtual drive.  I also put the second replacement in another bay and it appears as a foreign disk.   I tried using the 'replace member disk' option in OpenManage but no disks were listed as possible replacements and I got the following message: Storage Management only displays disks that can be used as a replace member. There are currently no disks that are available, large enough, or of the correct type to be used as a replace member for this virtual disk. The original disks are Dell 73GB SAS model #MBD2174RC.  The replacement disks are Dell 300GB SAS model #VJR75. Any assistance would be appreciated.    
Replace drive in PowerEdge 2970 RAID-1