WD10EARS replacement

I have a WD My Book WE II 2 TB, so 2 WDC WD10EARS-00M.  its tellig me that HDD1 has failed some diagnostic so I guess need to replace it.  Trouble is, with the shops around here, I can’t find the exact one. Closest I got is a WD10EARX and its only 1 piece left.  (1) Can I use this EARX given my firmware below? never really bothered on updates …and (2) will it still work if I have one EARS and one EARX? not currently running on RAID and planning to stick with just stripe.

01.02.04 with MioNet 4.3.1.13 
built on Fri May 28 11:15:28 CST 2010

Hello,

Sorry but you have to replace the internal drive with the exact same model in order to make it work.

thanks… so just confirming, I can use WD10EARX for this mybook - but I’ll have to replace both HDDs to be the same?