Network Address Translation/Default Gateway question

I have a PLC on a private network connected to a managed switch (AB Stratix 5700, which seems to be a rebranded Cisco IE2000) using 192.168.3.1 as the default gateway. This switch connects all of the ethernet/ip devices used in the control system. My goal is to translate the local IP address to a public address on our network using an Allen Bradley 9300-ENT (simple 1:1 NAT device), but have never done this on a managed switch.

I have two questions:

Will changing the default gateway of the PLC hinder the communication between other ethernet/ip devices on the private network?

I believe the managed switch has 1:1 NAT, but I am not sure where the public network uplink would go because the switch is connected to two more (unmanaged) switches via the dual-purpose uplink ports. Would any port on the unmanaged switches be sufficient?

Thanks for any help