Networking Help

[CIRCLE STUDY]

I am a Post graduate teacher wants to set my school LAN with Ubuntu so that i could give a common secured platform. For this I have loaded ubuntu desktop version in two of my machines in LAN, I have set up their IP suitably, they started pinging each other. Now the main problem is :

    i) How could I see the contents of one machine on LAN from another    ubuntu machine, on the same LAN, it was very much easier in case of XP , that one used to go to MyNetwork and was able to see all the machines in the LAN , and further he can roam the shared drives of other machine. But how should I do all that in Ubuntu. I am unable to find the documents of one machine from another machine, though they are Pinging.

ii) Is it compulsory to have a Domain setting for Ubuntu LAN configuration , isn't their any substitute for WORKGROUP Concepts of Windows over here.

iii) How to share internet between two or more Ubuntu Machine on LAN. I have a dsl-modem configuration on one of the Ubuntu Desktop on my LAN.

Kindly help me out. 
Kamal Kant Gupta  PGT (Comp. Sc.)   Kendriya Vidyalaya