MEK is a solvent used in plastics, it is what makes PVC pipe glue work.
It does not attack most paints, it is purchased in the paint department.
Get a small can and TEST it on your MH, the old paint on the surface may be weak and it may be a problem, if it is then tape and cover the paint or work SMALL area of the decal.
Since most fittings on the MH are plastic make sure you stay away from them.
Wax up the painted areas arround any work to be done with at least 3 coats.
Use purple gloves and have glasses on, a helper is handy.
It is not the safest thing to use, READ ALL of the warnings.
This stuff will instantly weld back cracks in white plastic, handy to have.
Now that the warning is done, here are the instructions.
Get a small bowl, brush and a plastic putty knife, apply the MEK lightly to the decal with the brush, it will soften, keep applying to insure it stays wet, the helper keeps the drippings wiped up to avoid issues with the paint, wax will be first protection from spills.
When it gets soft scrape with the putty knife, when it is just right it will peel off like a banana peel.
Keep the area free of spilled or dripped MEK, it should not bother the paint, but it is best to keep it clear.
We removed the decals from our old trucks this way, we just brushed it on and let it drip where it may, but they were only a few years old and good paint, I am not sure what your paint will do, but this process will not have heat damage or scratches.