Protecting your DATA should be your #1 goal and being parinoid is not a bad thing. Your data is safe and you can find it by attaching your drives to a client and set the client to be able to view Hidden Files and Folders. Your data will be in the hidden folder DE on your storage pool drives.
I would recommend you backup your data to a media of your choice but not all data we store is important but only you can determine what is and what is not important. A true backup means you have more than one location to obtain your data the server would be a location another would be say on a client but better if the data is stored say offsite say on backup drives, the cloud or optical media. Files that can be found on the internet or easily obtained from other sources is generally not important data because they are eaily obtainable but again the choice is yours.
Server recoveries are performed everyday without issue and when issues arrise then those individuals will come to sites like this to seek help. I have performed my fair share of server recoveries for one reason or another and I never take them lightly because WHS is sensitive to drive issues. With this in mind I always have a need to know if my drives are in good working order so I would encourage you to verifiy the drive are in good working order but with 8 drives its time consuming. Running a simple chkdsk on the drives while attached to a client will help you to determine if the drives are in good working order and if they need to be repaired in which CHKDSK /r comes in handy.
In addition to CHKDSK there is a new program out that you can install called WindowSmart2012 which will examine the SMART Data on your drives and let you know what condition they are in.
http://www.dojonorthsoftware.net/TBM/WindowSMART.aspxThe issue you have with 8 drives is just how much data do they contain and can you easily back the data up to other drives or media. Some like to install new drives into their servers and simply copy the data back to the server and then backup the data to a location of their choice then when the drive is free and the data safely moved they will then install the drive back into the server as a storage pool drive and keep repeating until they have gone through all the drives. This is very time consuming and can be expensive but it will also provide you with the peace of mind you require and will certainly allow you to protect your data. Once you have your data in 2 locations and you continue to store data both on your server and another location then later down the road performing a normal Server Recovery will give you piece of mind knowing your data is safe because its on both your storage pool drives and on the server.
However data organization is equally important and will require a great deal of thought but again not all data is important but only you can determine what is and what is not important.
Keep in mind that when Microsoft write WHS they did have keeping your data safe in mind when they designed the recovery process and so long as you use Server Recovery then WHS will rebuild your storage pool for you. WHS will need to see all your storage pool drives and they must be in good condition for the recovery to work properly otherwise it can end up becomming a very frustrastating task which is why I highly recommend you take the time to verify your drives are in good working order.
At this time I would recommend you give your options some thought and determine which way you want to takle this task. I recommend copying your data to a safe location then add a drive to your server and copy the data to the server and then add the drive your working with to your storage pool. Its time consuming and can be expensive but in the end you will be better off doing it this way because it will provide you with piece of mind.
Good Luck and protecting your data is Job 1....