Say ports 1-4 on the switch are your trusted devices, 5-8 are your untrusted, and 9-10 are the LAN side of the router. There are other ways to do it but this is probably simplest and easiest to mentally map. Set ports 1-4 and 9 as access ports for VLAN 100. Set ports 5-8 and 10 as access ports for VLAN 200. Now you have two virtual networks hooked into one physical, partitioned by the router.
You then set up eth0 (port 9) as trusted LAN and eth1 (port 10) as untrusted LAN in the router, and give each an IP range (Separate subnets at a minimum). Now all trusted can talk to each other and all untrusted can talk to each other, but nothing together yet.
You then set routes and rules (port filtering, SNAT, DNAT, etc) for port access from either network to the other to finely control what ports are available to what. You do the same thing with eth2 which would be the connection from the router to the modem for internet access.
Not a full tutorial but hopefully that points you in the right direction.