Lots and lots of posts in this section about using PE parts. Do a quick search and you'll find lots of posts.
The best way I've found to cut them from the fret is to lay the entire fret on something hard (I use 6" ceramic tiles. They cost about 0.50 each at any home improvement or hardware store). Use an X-Acto knife with a #10 blade (not the pointed #11 blade but a round-tipped #10 blade), and rock the blade over the material to be cut. Once they are free from the fret you can carefully file the remaaining material off.
You will need to use either cyanoacrylate clue (CA) or epoxy to glue them. Regular model glues will not work.
The parts can be primed for painting using any primer that will adhere to metal, but clean the parts first. I use alcohol to clean them. If the parts are just to be glued in place (no masking or heavy bending) you can get away with not priming them. Acrylics, IMO, tend to work a bit better on PE than enamels since they tend to be a bit more flexible when they are dry.
One more thing, PE parts are very easy to lose. Be very careful handling them because they are easy to drop. Where possible avoid using tweezers or you'll find out what "Tweezerpult" means when they go shooting across the room.