If the clear plastic piece you are referring to is the center post cap, it simply lifts up. If the model number is correct, the cap is listed as item 23 in this parts drawing:
Sometimes it can become gunked up with detergent and/or softener residue which can make it a little difficult get off. If it is on too tight, you can try reaching it with a pair of pliers and gently pull straight up on the handle portion. Make sure you do not damage the cap is it is required to provide and air gap to keep water from entering into the gearcase (transmission) shaft.
If you need further guidance, the following link explains how to access and replace the agitator dogs:
The part number for the agitator dogs is included in the instructions I provided. For a little more, you purchase the entire cam assembly (which includes the dogs, the cam and the bearing) for about $8 to $10. It is listed as item 9 in the drawing I provided and the part number is 285809.
Replacement parts can be found at any of the following websites:
All these sites are reputable, offer great service and have competitive pricing, so shop and compare. The first three sites have helpful exploded view parts diagrams to assist you with locating and properly identifying the parts you may need.
If you have questions, please post back and let me know. I hope this helps you.