I try to keep watch for people needing help as I was helped a bunch by this site.
Other sites are good, but I believe this one has the most knowledge to be looked up.
It has been a while since I had the 470, I would not worry about doing anything else inside.
When I had a couple of 470's, the first thing that went was the power supply. So even now I keep a couple on the shelf, just in case.
Having a backup system for parts would be good if you plan on using it for awhile. If it is more then just a year or two until you find something else, I would be looking for spare parts. You will note in my Sig that I have (2) extra units setting in the boxes for spare parts, plus I always have the spare power supplies and always have extra new drives.
To PP3.
When PP3 came out I tried to upgrade and it flopped, I don't know why, but I had a hard time with the 470. I ended up doing a clean load with the PP3. And yes all the updates are still out their last I heard.
The PP3 update I remember came as disks and was offered for a limited time. I'm not sure what you found but it may or may not be Just an update or the full version.
I would defer to someone that may remember better then I. I know there are some threads on that update, back in the day.
But, I do remember that PP3 did not give you that much more and I was disappointed that I ended up completely redoing my system for what little I got from it, also, I believe that HP still rolls out an update online once you have it loaded with the original disks that brings it up to 3. I believe, don't quote me.
Either way, both versions will work as well.
The PC backups that you spoke of, I do believe WHS v1 did pc backups the best and still does, but you need to watch out on win7 / win 8 / win 10 pc as they may or may not have the "system Reserved" partition and that needs to be backed up as well.
I had all my pc's setup to just backup the c drive and not the reserved, big mistake, when you restore a pc with just the C you will end up with a drive that is not bootable without the repair/install disk and then you end up using some tools to recreate that small partition, it's a pain, it's a lot easier to just back it up.
Also, if your PC has a recovery partition, I would back that up as well.
My secret is keeping as much data on the server as possible, that keeps the pc backups small and fast and the data on the server, once you turn on file duplication on the folders is safe.
Once your up and running I would recommend two things:
1) Download the free smart addin so you can keep an eye on the drives.
http://www.dojonorthsoftware.net/dl/InstallHomeServerSMARTClassic.zip2) Figure out how you are going to backup your shared data on the server.
The backup of the server data needs to be outside of the server: Cloud, ext. drives, another server or non-pooled drives. But have some kind of a backup, as with any version of windows, things can go bad quickly.
I sync to another server monthly, I also use two non-pooled drives and backup the server 2-4 times a year and I have 1 non-pooled drive I keep offsite just in case of fire/flood/theft.
Backing up the server is as important as backing up the pc's.
Hope this helps, as I said, not sure on your PP3 find, but it was not that big of an upgrade anyway and I believe it will come in as a update from HP anyway. Once your up and running, get all the windows updates and all the HP updates which will take awhile.
Good luck and let us know how it's going.
_________________
[X510 CPU/RAM/
All 2 TB Red's] [X510 CPU/Sync'ed Backup/All 2 TB Hitachi's]
[X510 /2 in box]
[X710 LIAN LI DIY W2016E] Stablebit Drivepool [EX-503 LIAN LI 5-bay USB3 External]
Fear the Cloud