If you have VS already installed, you'll need SP1 to proceed. No need to install VS 2008 just for the SQL install.
Hope that helps.
Great little article, and the gotcha about the filestream fix should get added to the main article. I found that to be problematic.
If you are using a slipstream install, I would also make sure to do the 1) installer 4.5, 2) .net 3.5 sp1, and 3)filestream fix, then a reboot, then do the SQL install.