Hard drive issue on LS-WVL

[splasshh]

I own LS-WVLB4C and recently encountered I20 error (degraded mode), indicating hard drive 2 is having I/O error. I'd appreciate some advise from experts here:

• Can I be sure that replacing new hard drive will solve this issue? any safe way to check if it's not the issue with the NAS backplane connector? I don't have any computer to conveniently plug my suspected faulty HDD to.
• I was browsing hardware shop last weekend and looking at the Red WD HDD. I realize my current seagate 1TB Barracuda HDD is "slimmer". I found from the web there are two different thickness of 3.5 inch HDD: 1.9mm and 2.6mm. Should I be worried with compatibility issue? 
• If I delete my RAID1 (to make it RAID0), will it erase the data in the currently healthy HDD?

Thanks in advance for response.

[Eastmarch]

1. You can't, but it's WAY more likely that the drive is failed. Yank the bad drive, connect it to a windows machine, and run CrystalDisk Info if you want to be 100% sure. Likely a waste of time though.

2. LS-WVL should fit any standardized drive size. The thicker ones are actually fit more snugly.

3. Yes, don't do this. You've had one drive fail, so I'd make sure your backup is in good shape and stay with a fault-tolerant setup.

[splasshh]

Perfect Eastmarch. You answered all my concerns!