If you plan to do it, get a stitch ripper from a fabric store. I do a bit of sewing and I wouldn't suggest anything else. I've taken pockets off of clothing before and if you're careful, you won't scar things up that way. That said, embroidery is Serious Bizness. Mechanically done, it's done at a very high tension and so it may distort the fabric if you take it out. You might end up with a ghost image. If you're intent on doing it (which means that the clothing isn't too expensive or you'll toss it otherwise), then go very slowly and iron the area when you're done using steam. If you totally screw it up and don't want to toss it out, you can always do some DIY shirt modification with bleach or dyes and stuff.