I personally wouldn't try the hammer and block without heating insert from the backside first.

I do this for cupped inserts a well. Heat with heat gun from below and use your metal block. I don't think you really need the hammer. Just press hard and the heat dissipation from the metal block will reset the glue in seconds.(on CUPPED inserts, i use a custom metal die underneath in tandem with the block on top.)

I had many raised inserts on a Funhouse I recently restored, this Pinside thread was very helpful:

http://pinside.com/pinball/forum/topic/leveling-inserts

Put a playfield protector on it, problem solved.

I have heated and pressed inserts in before but my DE Star Wars was a different story. Those inserts would not budge even with heat. I was concerned enough that I stopped messing with them. With all the graphics over them, if you mess it up you just can't order a new insert to put in. I put a Mylar square over the edge of the insert to protect the paint for now and will maybe try again sometime.

If you have a scanner, scan and make your own decals. But I would Mylar like lonzo said and deal with it later or never.

I ended up doing this with my F14 - I leveled some of them but heating them. I actually removed them, sanded and glued back in. but most of the 'arrow' head inserts had cracks and I didn't want to risk completely breaking them as there are not any replacements available that I could find. Most of these were barely raised (did try heating and pressing some down). Applied a couple coats of clear with decals and then decided on trying out one of the playfield protectors as I didn't want to mess with adding anymore coats of clear.

In hind site I probably should have pressed on with more coats of clear to level the surface (did have an issue at one point with the clear and didn't want to fuss with it anymore (or make a really big mess of it)), but the protector seems to work just fine as well.