Swapping turbos with engine in the car is possible, but it´s a real pain. Last weekend I changed both turbos of a friends car (one was seized) with known good stock turbos. The hard part is to unbolt the manifold...one bolt is very difficult to reach...and when you have the manifold off...you know, you have to get the bolt back on (I didnt count how many curses I spelled, when triing it...2 hours for one bolt).