how to establish work network (LAN & WLAN)

i need the complete informaition (software & hardware) for establishing a work network please
my network consist of :
- about 55 users (PC's & PDA's)
- server (what type of server)
- sharing printers
- task app.
- HR app.
- outlook (or what do you recommend)
- the network will be connected to wired and wireless (WiFi and GPRS)

Can we assume this is for a school assignment?

No ... !
it's for my own work (y)

That's very difficult to answer in a forum, especially since we know absolutely nothing about your work place. I'll have to assume that you aren't a network administrator, or else you'd know how to do this already. If you don't have a network/system administrator at work, then my suggestion would be to hire an external consultant to analyze your company's needs and make a recommendation.