I'm interested in opening up a small network lab for my research work at my house.

For this i already have purchased the following:-

#3 Pc's
#1 linux(machine) functioning as a router having 2 NIC
#1 8 port switch
Patch cables as required.

Now,the thing is that getting all this to work. I want the (3) Pc to have an access
to internet as most important requirement for any kind of research work. As it should
be the only thing that needs configuring is the linux box and frankly i don't know a
shit about iptables. Like setting up a DHCP server and doing a NAT seems GOOD in theory
but in practice i dnt know much therefore i want you guys to help me out in how could i get my whole n/w established and running.Thank you

every setting in iptables is easily found on google.
on the workstations simply set the gateway to the linux box

if your not 2 good with linux (or dont want to spend hours playing with IPTables) i suggest you try (the Smoothwall Project) its a pre-configured Linux Router, Firewall, VPN, Content Filter System and a bunch of other stuff. and best of all it's free