Speedometer problem part 2

i bought a gauge cluster at a junkyard for 20 dollars for my 94 civic. it has 30K more miles on it than my car actually has. are these things easy to turn back, or would I just be opening a can of worms if I went messing with it?

Is 20 dollars reasonable for one of these?

They are not easy to turn back, and yes that price is about normal.