i don't really think that recording videos can wear out drives, but thats just my assumption. regardless, you should get the newest gen wd black (goes by model wd#003fzex where # is amount of tb) instead of previous gen (goes by model wd #002something where # is tb)
about the ram, there is only a performance difference between 4x4gb and 2x8gb in systems which run ram in quad-channel mode, like the x79 chipset. the z87 runs in dual-channel so no difference. 2x8gb is a bit more expensive by like 10 bucks but its worth the upgrade capability in the future