Assuming pool is called "tank" and drive to be replaced is "da11":

1. swapoff /dev/da11p1
2. zpool offline tank /dev/da11p2
(This ensures that no system component is referencing that pool; after
this step the pool would be in 'DEGREADED' state).

3. pull out the drive, insert new drive, wait for drive to appear.
4. make the same partition layout:
gpart create -s gpt da11
gpart add -b 128 -s 4194304 -t freebsd-swap da11
gpart add -t freebsd-zfs da11

5. zpool replace tank da11p2
6. swapon /dev/da11p2
7. zpool detach tank da11p2/old (*)