ETH is generally pretty stable. I was not expecting it to get this high, this soon, and I also anticipated that it was possible that it would never crack $40 due to the large volume of ETH in circulation (as opposed to deflationary crypto like BTC).
When ETH cracked $50 recently (and then retreated to maybe $45, before returning to $49 where it sits now), it made me realize that it has the potential to go much higher after PoS. Though I am hesitant to make many predictions in that regard.
Failing any major negatives from the Vitalik and company, I do not expect it to drop. Every time whales try to drive it down, "bargain hunters" jump in to buy more and bolster the price. There are a lot of crypto investors out there that are keeping it above the $45 mark just on instinct.
There is also the really weird possibility that ZEC and ETH may merge once Vitalik's crew implements zk-SNARK into the Ethereum code base, which he has said that they will do. It's only a matter of time. We just don't know how long.
The ZEC guide is still basically accurate, it's just that you will not want to use Ubuntu 15.10 at all with 480s. I would recommend 16.04 with AMDGPU-Pro. Be sure to set it up to login automatically at startup rather than forcing you to login manually . . . that will make automation easier.