Need instructions/advice for best practice

I have an untangle 11 box setup in ROUTER mode.

External interface is WAN

Internal interface is 10.0.0.0/24

I have a PC that is statically assigned a 192.168.3.x address on the "dumb" switch connected to internal interface.

Is it possible for that PC to connect to the internet configured this way?

Would a VLAN be the best way to do it? Would I need a static route? Both? Neither? Can't be done?

Also, what would be the best firewall rule to allow only port 80 traffic inbound on internal interface if the source is WAN/external.

Thank you