I suspect you have the HD located in the optical drives location. If you do you HD likely died from shock. The problem here is the original HD does not have crash protection within the HD. Instead Apple has it as part of it's logic board HD SATA port.
So basically you want to locate a HD that has crash guard to replace your HD. In any case the slower RPM drive will be fine.
The other option here is to go with a SSHD unit replacing not only your HD but you SSD as well. While that may seam to be going backwards in truth it's going forward. Putting the SSHD in HD's location will give you a faster conduit as the HD SATA port is faster. In addition, the power requirement will be less giving you more battery time. Lastly, the performance will in fact be better than the two drive setup. Checkout Seagate's laptop SSHD's we have quite a few in use and love them.