I'm using the bezier tool, but I forgot the 'shape' option was set to an ellipse so my drawing is just a mess. Is there any way to change the shape option AFTER I've completed the curve?
Select the path and open the XML editor (Edit -> XML Editor).
You will note that there are more attributes in your path than on a simple path with no stroke shape.
In particular, click on
inkscape:path-effect and delete it (there is an icon with a red cross nearby).
Then you have the
d attribute, and the
inkscape:original-d attribute. The latter contains your path, while the former contains the complete shape of the stroke.
inkscape:original-d attribute, copy it's value, then select the
d element and replace its value with the copied path. Save this new value with the Set button.
Now delete the
You may need to set No-fill and a stroke color to see the path as a line instead of a filled-in area.