SETTING UP UBUNTU SERVER

Dear All,
I am trying to setup UBUNTU SERVER for official purpose. I could make a simple server. But i should aware before setting up UBUNTU server. If something goes wrong in future i should be able to recover server data.

My server is simply for FILESHARING. Please give me some guidelines before setting ubuntu server.

I have 500GB HDD. I planned to split thd HDD as / 50GB, /data 400GB /swap 3GB.

I wanted to store data separately in /data drive.

Please let me know if i am in a situation to reinstall the server will i lose the /data data?

And after setting the server i would like to move all the data from WIN2003 to UBUNTU SERVER. But there is no GUI in ubuntu server. How can i get GUI and to transfer data?

Thanks for all.