With regards to pack covers and such, there are several different options.
A standard backpack cover is useful when hiking in the rain for obvious reasons. These do tend to get damaged when backpacks are not worn, such as when being carried by llamas and mules.
A water proof duffle bag can be very useful in this situation.
We will be using waterproof plastic trash bags inside our backpacks and these are far more important for keeping your clothes and personal belongings dry.
A rain cover on your day pack will be extremely practical. Most come with these packs and can be found in a zipped section at the bottom of your pack. They can also be bought separately. Just make sure that it fits well.
I hope that helps. Enjoy the packing and get excited.
Nos vemos pronto!