Replacement part for a stanley bifold mirror door

​Hi my name is Mathew, I have a Stanley bifold mirror door which is running on 2 tracks ( one upper and another bottom) and the door runs in the tracks on white plastic roller, one of the plastic roll is broken, I found a roll
( #21-174) in the website , i want to make sure that I found the right part, I am sending some pictures with this. Another question is- in order to change the roll should i remove the door with both tracks and install the roll and put the track and door in place?