new routers come with a quick setup instructions. we can help once you buy it.
you only need the 54mbps... wii doesn't support the 802.11n or suped-up 802.11g.
what will really matter is keeping the router relatively close so you don't drop in thoughput, like 802.11b speeds or even as low as 1mbps. other than that, your broadband ISP could offer bottlenecks during peak hours.