So far so good. What's the next step to get the network card running? I assume I'll just install the driver, tell the Genesis Wizard to use it and I am done? Does AmTCP/Genesis support DHCP?
AmiTCP doesn't have DHCP support, so you'd need to have static IP addresses. If it isn't possible, then you could get some few bucks router in between to do the job. Or change tcp/ip stack to Miami or wait till next year for Roadshow.
Your PCMCIA card migth also not work directly because of the PCMCIA reset bug on A1200. Card shoud start working if you hotswap it when computer is on and for longer term fix you should install cardreset/cardpatch fixes from Aminet.
Otherwise setting up the TCP/IP stack should be pretty straightforwarded as you already guessed. Install the driver and configure the stack.