Mel,

By the title of your post, I'm assuming these are decals. Also,
assuming you've purchased a glass ship.

The letters I've worked with come off reasonably easily with plain old
mechanical methods (ie. peeling). It may help to use a heat gun on
LOW to soften the adhesive and material a little, but be very careful
not to get the surface too hot; if it's too hot to comfortably touch
it's too hot. You can use a plastic scraper to help things along.
The kind sold for mixing up plaster or bondo honed to a sharp point
work great. Final cleanup with a little bit of acetone on a rag
followed by a rinse with some H2O will get rid of any residual
adhesive.

Hope this helps.

Erik Mann (P3)