One great feature of the parts list is when you swap parts, Civil 3D automatically re-assigns a style based on what you've assigned to that part. FYI - Don't get too spoiled with this feature because it doesn't work in cases where the pipe or structure is a data reference. The part swap will come across just fine when you synchronize, but the style change will not. You'll have to manually assign a new style through Pipe/Structure Properties.
I have only verified this behavior in r2010 so if you have r2011 handy, try it out and let us know if it works differently.