I have a snapper 33inch rider about 3 yr old.. I hit a water outlet and bent the blade real bade.. I bought a new blade and a new blade holder but I can't remove the blade holder to attach the new blade. The mover cut with the new blade but tends to have more vibration then it had before. How can I tell if the shaft is bent or just the blade holder

What exact model do you have? Maybe we are just saying this differently but the holder does not come off to replace the blade, you just remove the two bolts in the blade. http://www.searspartsdirect.com/partsdirect/part-model/Snapper-Parts/Riding-mower-tractor-Parts/Model-YZ16335BVE/3290/1506000/P0809010/00012 When you hit something and get vibration it can be from any one of theses issue starting with the first most frequently" bent blade, bent spindle, bend crank shaft. The only way to rule out a bent crank is to remove the blade and the spindle. If you still have vibration your crank is shot.

I have a Snapper 331723DBE. The blade is attached by two bolts to a bar (threaded blade holder) that attaches to the spindle shaft. Is there an easy way to get the blade holder to come loose from the spindle?

Did you open my link, it has a diagram of your spindle. Remove the blade first and then the one large bolt centered on the spindle