This is feasible and direct attached tape is not uncommon.
BE will control the tape robot with NDMP commands that pass through the 3020 to the tape library so tape moves should all work from the master server gui.
The FAS3020 will not need a restart. Make sure to connect the library to an FC initiator port. Many libraries export robotics over the same port as the tape drive (not sure if this tape library has a separate FC connection for the robot or not, but if it does, just run another connection to the 3020), so often we can connect tape and robot with one FC cable (with different LUNids). If multiple tape drives, it is one FC cable per drive, so if more than 2 a switch starts ot make more sense.
Also, if you are using a PCI FC Card for this, make sure that port pairs (a/b and c/d) either connect to only disk or only tape. For example a/b to tape and c/d to disk is ok, but a to tape and b to disk is not ok. If you are using onboard ports 0a/0b/0c/0d there is no issue with this (0a can be on tape and 0b can be on disk)... this only applies to expansion cards where the ASIC that runs the port pairs on each card should not mix disk/tape. Since there are 2 asics on these cards, you can mix across port pairs. Here is the KB article on this https://kb.netapp.com/support/index?page=content&id=3011912
Once you attach the library, you can confirm tape and the robot with these commands
Tape Drives
3020> sysconfig -t
3020> storage show tape
Medium Changer (robot)
3020> sysconfig -m
3020> storage show mc
Check aliases
3020> storage show alias
If you have never attached tape before, surely you will have "mc0" for your robot and "nrst0a" for your tape drive. Use these in BE setup. Use the no rewind device (nrst0a) instead of the other devices... If you don't see the alias for tape, then you may have an "unsupported" drive and need to create a tape_config file but wait until you connect and check... often for half height LTO drives we have to create the config file.