at home im running ubuntu server edition 8.04 its used to back up my servers websites via ftp works a treat.

I read somewhere you can install the Ubuntu GUI on top of the server however if i did this what effects would it have on performance.

I would like to be able to play around with ubuntu but dont want to break the system.

If i installed the desktop would i still be able to use command prompt for the server ie ssh, would everything still be the same as before.

I have never played with linux and would like to learn basic think such as installing programmes and so on.

Any advice would be appreciated, however dont ask me to use virtual PC to play around i dont like the idea of running vista and virtual pc it just does not feel the same and dont get the speed.

The desktop is just an add-on, it will not break anything. If you are worried that it might affect performance, then you could set things up in such a way that the desktop does not run unless you launch it manually.

Just be aware that xorg is a network application and a door open to your server if you don't close it.

Yes. But you should bear in mind that the same would be true if you got the normal ubuntu install and added the server processes that you want to add (in theory, there are probably server optimisations that the server kernel has, but whether you would ever notice their abscence unless your needs are for a high throughput server, which I suspect yours aren't).

Sounds interesting how would i go about such a setup where as the desktop will only load should i want it to.

and how do i go about installing the GUI

http://ubuntuforums.org/archive/index.php/t-186298.html

As for controlling X manually, there are various ways of doing so. You could not install GDM, you could stop it or you could even disable it.