I'm not sure which model you have, but I have the Next Generation Quilting frame (metal)
To remove the plastic track, just poke a screwdriver in the end and pull it up. Now it seems to me that I inquired a long time ago about replacing my tracks with metal ones and they were not available for this particular model so I don't know how they would on.
As for the wobble - is your floor uneven? Use a level to ensure that it is level horizontally and also set the level where it is attached in the centre to ensure that it is not sitting at a slight angle.