We have a Murray LawnTractor and need to change the front tires. Having troulbe removing the hub cap. Can this be done without destroying the cap?

Hi,
It does not matter if it is soft or hard plastic, both will come off. Both just fit over a washer to hold them on.
Hard plastic should pry off, Soft plastic can shrink and get stubborn with age; sometimes prying or getting something under one spot. I have used a pair of slip-joint pliers, grabbed the center and slowly and forcefully wiggled back and forth.
Peace,
Clarke