It looks like you have your path laid out and now you just need to add a cross section for the sweep. Just sketch a circle (or two concentric circles for a wall thickness) and then use the sweep command and select your path and cross section sketches and you should be good to go.
See this video, and if you like the idea can use ST to create pipes without having to draw the lines or curves. This will need a little practice but I found it very appealing and powerful and also relevant to your question:
Tushar, are bend radii changeable with this method?
Darren, here's a small video if it helps you.
The derived curve may not be necessary in your case if you are on ST7 and if a 3D curve can be used as path.
@bshandI am working on your question.
with ST7 You will find the 3D sketches.
They make this task a lot easier.
I would agree that 3D sketches are the way to go. About time SE features that capability.