No you would have to reinstall so windows 8 can set this up on install, after you update the firmware on your SSD to support edrive
To be honest I would test the software version of bitlocker and see if there is any negative impact - I have it activated on all my windows machines and have never noticed it being slower.
For the software version no you wont need to re-install windows, just make sure bitlocker has finished encrypting before a reboot.
Bitlocker always asks for a password at boot to unlock the drive