I am not sure if you just want to change the trim scheme or replace all the covering on the plane.

If it is just the trim scheme, I suggest using a TRIM IRON to heat the trim and while still applying heat, peel the trim off. Then use some acetone to rmove any remaining glue and/or fingerprint oil from the covering. Reshrink the covering and apply your new trim scheme.

If you want to recover the plane, use a HEAT GUN to soften the adhesive and peel the covering off while applying heat. Carefully sand any areas that still have pieces of covering still attached to get the airframe smooth. If you are covering in a darker color than was initially on the plane you are OK. If you are doing a lighter color, go over all the areas that have the color leached into the wood with some 220 paper to remove all the color so it won't bleed through (show through) the new covering.

FWIW - This ONLY WORKS for Monokote. Spray the area you want to apply the trim to with blue Windex, them apply your trim and carefully squeegee out any excess liquid. Let dry for 24 hours, then go over the edges with either a trim iron or Monokote trim sealer to seal the edges down.