I didn't remove my intake manifold to do my injector seals although working space was minimal. You will need a pry bar of sorts to get those injectors to pop out. You will have to get the shrouds from a VW dealer or from http://www.autohausaz.com.
I have no experience with oil pressure problems so I don't know the answer to your question. I wouldn't drive the car if your oil pressure is in doubt. That napa oil pressure switch looks right. The switch is cheap so it's an easy place to start.
Maybe someone can chime in here with some beta on oil pressure/sensor issues.