From what I understand, I have 3 options: 1. Keep the HDD and add an SSD. But this requires removal of motherboard and many other things, right? 2. Replace HDD with SSD. This requires an optibay and once the iMac is open, just swap out the HDD with SSD, correct? 3. Use an external SSD. From what I've seen, these are more expensive and they seem more inconvenient in the long run. Is it true that these are my only options for self install?