Create a sequence with the settings you want (the correct settings).
Return to you original sequence with the incorrect settings and click anywhere on the timeline.
Type Command + A to select all the clips.
Once selected, type Command + C to copy the clips.
Now go to your newly created correct (empty) sequence, and click anywhere in the sequence.
Type Command + V.
If the clips are distorted or sized incorrectly in the new sequence, click anywhere on the timeline and type Command + A to select all the clips.
One selected, Control-click on any one of the selected clips, and from the drop down menu choose "Remove Attributes"
When the Remove Attributes pane opens, check the boxes for Basic Motion and Distort, if available.
Click OK. This should modify all the clips that were selected (the entire timeline).
Does this help?