Can I have multiple versions of the Windows SDK installed and switch between them?

Yes!

when you compile in Visual Studio it will give you the option of which SDK to link to. sweetness.

Windows SDK errors about incompatible versions...

Got an error along the lines of 'hey, your version of the Windows SDK is newer than the one this project/solution was built with', retarget the solution or the projects. Trying to use the retarget option off of the right mouse menu for the solution did not work. Going to each individual project (thank goodness there were only three of them!), select properties, select a new 'Target Platform Version' seemed to get me through this issue.