ReadyNAS NV+ Drive 4 Failing

Hi All

I am running system below

Model: ReadyNAS NV+ [X-RAID]
Firmware: RAIDiator 4.1.8 [1.00a043]
Memory: 256 MB [2.5-3-3-7]
Volume C: Online, X-RAID, 4 disks, 52% of 5560 GB used

Been running it for 2 years now running 4 x Seagate HDD 2TB Model - ST32000542AS.

Drive 4 is now having errors below

Model: ST32000542AS
Firmware: CC34

SMART Attribute

Spin Up Time 0
Start Stop Count 57
Reallocated Sector Count 113
Power On Hours 8565
Spin Retry Count 0
Power Cycle Count 57
Temperature Celsius 36
Current Pending Sector 0
Offline Uncorrectable 0
UDMA CRC Error Count 433
Head Flying Hours 80406082757101

ATA Error Count 0

Extended Attribute

Hot-add events 0
Hot-remove events 0
Lp stat events 1
Power glitches 0
Hard disk resets 0
Retries 0
Repaired sectors 0

1. Should I replace HDD # 4?
2. If I have to replace HDD # 4 I cannot find the same model HDD to replace the original. Can I replace it with another 2TB HDD on the HCL?
3. Or is there something else I can do?

Thanking all in advance for your time and help