What do you want, Client or Server? I know the 90/30 line has it internal to the CPU, both Client and Server. If you can't get it on Versamax - use a 90/30.
Yes. The Versamax does support Modbus TCP/IP protocol. You will have to use the VMSE (Versamax serial to Ethernet adaptor) For further details on how to configure the PLC refer to GE Fanuc manual GFK-1852 on the GE Fanuc website or visit http://www.gefanuc.com/infolink/manuals/gfk1852.pdf
You can use an IC200SET001, list around $350. It is an external device that bridges and ethernet connection to a RS232 or RS485 connection on the Versamax and supports Modbus TCP Server. You can go to the GE Fanuc website at www.gefanuc.com and read more in manual GFK-1852.