Do I need an special SCSI card?
You'd need another LTO-3 (or 4/5/6) drive yes and you can usually buy them with different connection type, though I'm not aware of there being anything as simple as say a USB or Firewire connected version. Most LTO 3 drives have a parallel SCSI 160 LVD connection so using one of those would require an appropriate SCSI card, I like Adaptecs ones. If you went for an LTO-4 or higher version they make SAS versions, which may be easier to deal with.
Could I use RedHat or Windows 2008 on PC? It would depend on the files
saved in the tapes?
I'd strongly advise using the same OS as the machine it was backed up from.
Would be any device to just plug on PC and lets read the tapes?
Not that I'm aware of, there might be a SCSI 160 LVD to USB/firewire converter but that may be as complex as just buying a SCSI/SAS card.