Dont use a sharp razor blade. Find a nice dull one, or a old dull pocket knife. Just be careful of the angle when removing fletch. Depending on what type of glue was used, it can be tough. The super glue (cyanoacrylate) type adhesives are brittle and tough to get off.
I think you will enjoy fletching you own. Just take your time. Do a dry run and make sure the jig is set up for the arrow properly, and that the vane contacts the arrow base evenly. The other trick is to make sure the bead of glue is even and contacts the whole base(no puddles or dry spots)