Value wise I think it depends on it's current condition
Is it completely mint then leave it.
Is it a routed game with scratch, marks, .. you can only improve it. If you can really do a good job you can only improve it.
Only if your new decals are really bad it will make the game worth less.
I had a wpt which I also considered re decalling. Cabinet had deep scratches but playfield was good. Now sold it, but had I kept it and redecalled then I would also have made new artwork for it.