It's easy to do mate, but be aware, if you remove it, the glue will leave a weird stain on the glass. It can be removed, but it takes a polishing kit to do the job properly.
As for fitting it, piece of cake. Cut it oversized so you have some wiggle room, heat the lights gently with a hairdryer, lay the Fly Eye over and jobs done
Any pics mate ?? also how does it effect lighting at night ??
Cheers