I need to buy some new hard drives for my Mac Pro

Question

I had an extra internal hard drive in my Mac Pro, a Seagate one, that suddenly stopped working and I needed to send it to a data recovery company, so...
Now I'd like to
- Install a new internal HD
- Install a NAS with two/three disks. (Hitachi if possible, as I have read are the ones that last longer, more reliable than WD and by far more than Seagate).
But to do that I'd like to know how to find out the right type of disks for my computer.
I'd be very gratefull if anyone would tell me where to look it up.
Thank you in advance
In case any of you can help with this, these are the details of my Mac Pro
thanks again
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Mac OS X Lion 10.7.5 (11G63b)
2 x 2.66 GHz Dual-Core Intel Xeon
Memory 7GB 667 MHz DDR2 FB-DIMM
Model Name:          Mac Pro
  Model Identifier:          MacPro1,1
  Processor Name:          Dual-Core Intel Xeon
  Processor Speed:          2,66 GHz
  Number of Processors:          2
  Total Number of Cores:          4
  L2 Cache (per Processor):          4 MB
  Memory:          7 GB
  Bus Speed:          1,33 GHz
  Boot ROM Version:          MP11.005D.B00
  SMC Version (system):          1.7f10
  Serial Number (system):          Not Available
  Hardware UUID:          00000000-0000-1000-8000-0017F20F9F40
+++++++++++++++++++++++++++++++++++++++++++++++++++++
The only HD now
Intel ESB2 AHCI:
  Vendor:          Intel
  Product:          ESB2 AHCI
  Link Speed:          3 Gigabit
  Negotiated Link Speed:          3 Gigabit
  Description:          AHCI Version 1.10 Supported
ST3250824AS  P:
  Capacity:          250,06 GB (250.059.350.016 bytes)
  Model:          ST3250824AS  P                         
  Revision:          3.BQK  
  Serial Number:                      9ND1P4X7
  Native Command Queuing:          Yes
  Queue Depth:          32
  Removable Media:          No
  Detachable Drive:          No
  BSD Name:          disk0
  Medium Type:          Rotational
  Bay Name:          Bay 1
  Partition Map Type:          GPT (GUID Partition Table)
  S.M.A.R.T. status:          Verified
  Volumes:
disk0s1:
  Capacity:          209,7 MB (209.715.200 bytes)
  BSD Name:          disk0s1
  Content:          EFI
HD INTERNO PRINCIPAL:
  Capacity:          249,2 GB (249.199.591.424 bytes)
  Available:          37,91 GB (37.914.918.912 bytes)
  Writable:          Yes
  File System:          Journaled HFS+
  BSD Name:          disk0s2
  Mount Point:          /
  Content:          Apple_HFS
Recovery HD:
  Capacity:          650 MB (650.002.432 bytes)
  BSD Name:          disk0s3
  Content:          Apple_Boot

Answer 1

NAS is of course external and depends on how you access it. And then t he ideal for RAID5 for instance woudl be WD RED series, but those do not work inside Mac tower.
Look up "TLER"  regarding WD drives and RAID.
Apple does not endorse or anything, not in decades and when there were problems - G5 and early adoption of SATA and changing standards and features, it was users that did the troubleshooting. 
So unles you are using Apple's PRO RAID card, which I don't think anyone would or should and which is limited to 2TB drives and only instance of a ceiling on supported drives (it is req'd for SAS though), use your own research.