Ok. I will wait till You will be able to follow the advice. If You want to re-write my instructions to make them more clear - please do.
By risky I meant that You might end up with no X server running on this installation. This means that there will be no clicky things - just a textual login. There is a little chance of this happening and yes - it can be fixed. The computer won't explode that's for sure.
I am sorry I am unable to teleport myself to Texas for a few minutes and help You with it personally. It would be fixed in a few and I could teleport myself back to the green island
By risky I didn't meant that any other installation will be affected. Btw - by other install do You mean another installation on another partition or just another Desktop Environment on the same installation? I need clarification here. If it's another installation on another partition then it won't be affected.
Well... Not sure what other think about this situation. So far noone else posted any advices...
Hope I have helped.