new network admin

i am new network admin and i am asked to present a proposal to fully manage ,control,and secure the current network infrastructure.
the current status of the network is 130 clinets attached to the network and a DSL connecting all clients to the internet directly through a switch.
my proposal is to setup the following:
1- domain server
2- antivirus server
3- exchange mail server
4- i may install database servers for backup purposes.
plz would some person help me to design the network and how the traffic will be handeled?