2009 Hard Drives - time for replacement

[DLI]

My Linkstation Pro Duo (LS-W2.0TGL/R1) has two 1 TB Hitachi drives made back in 2009.   One of them is starting to die, throwing up some errors (I forget what error exactly as I have pulled them from the LinkStation - after backing up the data).   My goal is to do 2 things.
a) replace these drives with new 2 TB drives
and
b) completely erase these drives so they can be sent off the recycle depot

A few questions ..
1) is 2 TB the max I can put in this old LS?  I plan to put them in Raid 1 config.

2) how do I remove the data on each of these old drives?  I can't seem to connect to them via standard windows OS so I can read/format/erase (would like to use DBAN)