Here is my own suggestion :-
For sql server make backup of database and for Visual studio make backup of settings. Settings can be accessed through My document/Visual studio 2012/Settings Same way you got settings for sql server management studio.
Having backup of setting make it easier to move to new version. Now uninstall both and restart your computer.
After restart install both thing. It will be worked.
if you want both version you can have it. Both software provide side by side installation. Remember that you maybe got some panic experience to have two database server on same computer.
You can 2008,2010 both version without any conflict.