Just like kuksul08 stated. If you want to have the performance of an SSD and the capacity of an HDD, you may need to sacrifice your CD/DVD drive for the extra space to mount a second drive in there. They make adapters and holders for that exact purpose so in terms of reliability, you should be golden.
As far as screen goes, resolution is king and everyone is going to tell you that based on the needs that you established (i.e 50+ GB of HD GoPro footage) so resolution is a must but also for more usable space. Im sure with those needs, you probably have a higher end program to edit the vids so having more menu bars and such along with a large work area is going to be key.