Seting up WLAN

HI,
My company is in the process relocating,and I wld like to setup WLAN, as am not that familiar with it,need advice on how to proceed,
I’m planning to have the backbone to be wired,
the client nodes to be wireless ,
Am planning to connect 30 Nodes,
can anyone tell me how many access points I need?.
The office layout is one big room measuring 40M*20M.
and is there any good websits I can refer for more indepth info.
thanx in advance