Hi Rixchard,
I haven't found a convenient solution yet, but you may want to try this...
I recently built my Matchbox 1/72 Hawker Tempest V kit which I bought since I was in high school [:0]. Same as with your piece, the covering paper has stuck to the decals, maybe due to humidity. I didn't know how to fix the problem so I experimented, reasoning that if I ruin these decals I can always go for AM ones. I decided to soak the whole decal sheet in warm water, and sure enough, after a few minutes, all the decals were set loose from the backing paper as well as the cover sheet. A little scraping with my fingers got off some stubborn paper fibers as well as glue on the surface of the decals. I arranged the salvaged decals onto a sheet of good old wax paper then put the whole sheet into a sandwich bag for keeping till my decaling session. Yes, the decal glue was diluted and almost gone but that is not a problem since I can use diluted white glue or even Future to secure the decals to the model. Come decaling time I did just that and applied MicroSol and everything came out dandy. A protective coat of Future sealed the decals and blended them with the model. You wouldn't know by looking that once those decals had paper fibers "growing" out of them!