I am quite new to SolidWorks and need what is probably some basic help.  I created the assembly pictured and what I want to do is model a piece of tubing referencing the geometry in the assembly.  In this instance, I want the tubing to connect the two fittings shown following the arc in blue.

My approach has been to start a 3D sketch and draw the path shown in blue.  I then exited the sketch and created the profile in a separate sketch.  So far so good, but at this point I want to sweep the profile along the path.  I'm still in assembly mode, so my sketch doesn't show up as a part where the features are available to sweep.  If I first try to insert a new part and then sketch, I can't seem to reference the existing models to draw my path.  Does that make sense, and what am I doing wrong?

Thanks,

Mark